MVP refactoring for funfacts

[Niranjan-B]

1. Refactored FunFacts activity into MVP style.
2. Changes in FunFactFragment - (i) initialised ButterKnife to get the FAB click-listener working, (ii) concatenated ".png" to the saved screenshot file name to avoid "Format not supported" while sharing on WhatsApp and other apps.

[Niranjan-B]

Hi @Swati4star , the build is failing with the message -> "You have not accepted the license agreements of the following SDK components:
[Android SDK Build-Tools 25.0.1, Android SDK Platform 25].
Before building your project, you need to accept the license agreements and complete the installation of the missing components using the Android Studio SDK Manager."
The build fail might be because of the differences in Android build tools, Android SDK used by the project and Travis environment. I can change the .travis.yml file and re-push if you want me to?

[Swati4star]

Yes please. Modify the .travis.yml file.