detect incremental compilation

Conflicts:
	src/main/groovy/me/tatarka/RetrolambdaPluginAndroid.groovy
	src/main/groovy/me/tatarka/RetrolambdaPluginJava.groovy
	src/main/groovy/me/tatarka/RetrolambdaTask.groovy
change java plugin to correctly detect incremental builds
updated retrolambda version to one that has incremental compile support
incremental builds working with android
working on library projects now
bump version
updated the README
moved updates to CHANGELOG.md