updated build tools version to 19.1.0
Merge pull request #53 from cutmail/update-buildtools-version

Updated build tools version to 19.1.0
Refactored Gradle build files and removed sdk versions from AndroidManifest.xml.
Merge pull request #54 from edmodo/update_gradle

Refactored Gradle build files and removed sdk versions from AndroidManif...
Support to publish cropper to maven repository.
Fix artifact packaging containing "aar.asc" ext.
Bump maven lib version to 1.0.1.
Merge pull request #55 from edmodo/support_maven

Support to publish cropper to maven repository.
Update README.md