Beta 3

• Improve DynamicMapLayer panning and zooming performance. #137
• FeatureLayer and ClusteredFeatureLayer can now load features from map services. Thanks to @odoe and @jgravois.
• FeatureLayer, DynamicMapLayer and ClusteredFeatureLayer all accept a token option for accessing services that require authentication and fire a authenticationrequired event when they encounter a need for a token. Thanks to @aaronpk for the Oauth demos. #139
• Add DarkGray and DarkGrayLabels to BasemapLayer. #190
• An attributionControl on maps is now required when using BasemapLayer. #159