0.1.3

• Add non-null pre-condition check.
• Add javadoc for MarkerDragEvent.

Java bindings:

compile 'org.aaronhe.rxgooglemapsbinding:rxgooglemapsbinding:0.1.3'

Kotlin bindings:

compile 'org.aaronhe.rxgooglemapsbinding:rxgooglemapsbinding-kotlin:0.1.3'