Update README.md

Added the correct link to play store.
Update README.md

Using Markdown fpr play store linking.
Merge pull request #2 from atomfrede/master

Correct Play Store Link in Readme
Merge pull request #9 from devisnik/master

enable action mode on long-pressing links
Update licensing to be Apache 2 across the board
Add Twitter4J in the readme credits. Not sure how I forgot that...