Update README.md

rename exlang to WikiCards.
bug-13 create WikiCards project.
Merge pull request #1 from thomas771020/bug-13-new-project

bug-13 create WikiCards project.r=hchu
bug-14 relayout the activity_main to landing page
Merge pull request #3 from john-hu/bug-14-landing-page

bug-14 relayout the activity_main to landing page, r=thomas.