update to modern use of `instancetype`

@@ -122,7 +122,7 @@
 *   @param aCoordinate The location for the annotation. 
 *   @param aTitle The annotation's title. 
 *   @return An annotation object, or `nil` if an annotation was unable to be created. */
-+ (id)annotationWithMapView:(RMMapView *)aMapView coordinate:(CLLocationCoordinate2D)aCoordinate andTitle:(NSString *)aTitle;
++ (instancetype)annotationWithMapView:(RMMapView *)aMapView coordinate:(CLLocationCoordinate2D)aCoordinate andTitle:(NSString *)aTitle;
 
 /** Initialize an annotation. 
 *   @param aMapView The map view on which to place the annotation. 

@@ -55,7 +55,7 @@
 @synthesize clusteredAnnotations;
 @synthesize isUserLocationAnnotation;
 
-+ (id)annotationWithMapView:(RMMapView *)aMapView coordinate:(CLLocationCoordinate2D)aCoordinate andTitle:(NSString *)aTitle
++ (instancetype)annotationWithMapView:(RMMapView *)aMapView coordinate:(CLLocationCoordinate2D)aCoordinate andTitle:(NSString *)aTitle
 {
     return [[self alloc] initWithMapView:aMapView coordinate:aCoordinate andTitle:aTitle];
 }

@@ -49,7 +49,7 @@
 *   @param aTile The tile key for the object.
 *   @param aCacheKey The unique identifier for the cache.
 *   @return A newly created cache object. */
-+ (id)cacheObject:(id)anObject forTile:(RMTile)aTile withCacheKey:(NSString *)aCacheKey;
++ (instancetype)cacheObject:(id)anObject forTile:(RMTile)aTile withCacheKey:(NSString *)aCacheKey;
 
 /** Initializes and returns a newly allocated cache object for a given key and object to store in a given cache.
 *   @param anObject The object to cache, typically a UIImage.

@@ -42,7 +42,7 @@
 @synthesize tile = _tile;
 @synthesize timestamp = _timestamp;
 
-+ (id)cacheObject:(id)anObject forTile:(RMTile)aTile withCacheKey:(NSString *)aCacheKey
++ (instancetype)cacheObject:(id)anObject forTile:(RMTile)aTile withCacheKey:(NSString *)aCacheKey
 {
     return [[self alloc] initWithObject:anObject forTile:aTile withCacheKey:aCacheKey];
 }

@@ -34,7 +34,7 @@
 
 /** Access the shared instance of the configuration. 
 *   @return The shared configuration instance. */
-+ (RMConfiguration *)configuration;
++ (instancetype)configuration;
 
 - (RMConfiguration *)initWithPath:(NSString *)path;
 
@@ -65,7 +65,7 @@
 
 @interface NSData (RMUserAgent)
 
-+ (NSData *)brandedDataWithContentsOfURL:(NSURL *)aURL;
++ (instancetype)brandedDataWithContentsOfURL:(NSURL *)aURL;
 
 @end
 
@@ -73,6 +73,6 @@
 
 @interface NSString (RMUserAgent)
 
-+ (id)brandedStringWithContentsOfURL:(NSURL *)url encoding:(NSStringEncoding)enc error:(NSError **)error;
++ (instancetype)brandedStringWithContentsOfURL:(NSURL *)url encoding:(NSStringEncoding)enc error:(NSError **)error;
 
 @end

@@ -46,7 +46,7 @@ static RMConfiguration *RMConfigurationSharedInstance = nil;
 
 @implementation NSData (RMUserAgent)
 
-+ (NSData *)brandedDataWithContentsOfURL:(NSURL *)aURL
++ (instancetype)brandedDataWithContentsOfURL:(NSURL *)aURL
 {
     NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:aURL];
 
@@ -61,7 +61,7 @@ static RMConfiguration *RMConfigurationSharedInstance = nil;
 
 @implementation NSString (RMUserAgent)
 
-+ (id)brandedStringWithContentsOfURL:(NSURL *)url encoding:(NSStringEncoding)enc error:(NSError **)error
++ (instancetype)brandedStringWithContentsOfURL:(NSURL *)url encoding:(NSStringEncoding)enc error:(NSError **)error
 {
     NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
 
@@ -92,7 +92,7 @@ static RMConfiguration *RMConfigurationSharedInstance = nil;
 
 @synthesize userAgent=_userAgent;
 
-+ (RMConfiguration *)configuration
++ (instancetype)configuration
 {
     static dispatch_once_t onceToken;
     dispatch_once(&onceToken, ^{

@@ -43,8 +43,8 @@
 // applies #wrapPointHorizontally to aPoint, and then clamps northing (Y coordinate) to projection's planetBounds
 - (RMProjectedPoint)constrainPointToBounds:(RMProjectedPoint)aPoint;
 
-+ (RMProjection *)googleProjection;
-+ (RMProjection *)EPSGLatLong;
++ (instancetype)googleProjection;
++ (instancetype)EPSGLatLong;
 
 - (id)initWithString:(NSString *)proj4String inBounds:(RMProjectedRect)projectedBounds;
 

@@ -50,7 +50,7 @@
 static RMProjection *_googleProjection = nil;
 static RMProjection *_latitudeLongitudeProjection = nil;
 
-+ (RMProjection *)googleProjection
++ (instancetype)googleProjection
 {
     if (_googleProjection)
     {
@@ -66,7 +66,7 @@ static RMProjection *_latitudeLongitudeProjection = nil;
     }
 }
 
-+ (RMProjection *)EPSGLatLong
++ (instancetype)EPSGLatLong
 {
     if (_latitudeLongitudeProjection)
     {