Remove allowBackup attribute on AndroidManifest

Fixed issue #21

Fixed months calculations and updated/refactored dependecies

From now on this library needs to be compile with Android Studio 3.0.

fixed month calculation;
refactored dependencies:

• removed ButternKnife
• removed Retrolamba
• changed to Java 8
• updated build tools and android support libraries to 26

v0.1.3

Added the possibility to format the days names

v0.1.2

v0.1.2

v0.1.1

Merge branch 'develop'