Few minor fixes, and a cleaner README

So, call me pedantic, but:
a) The 'View Stats' button for all the projects was slightly off center. Changing the 'left' style element to 22% fixed that. But it also screwed the 'GitHub' button on 'Your Project'. Adding an inline 'left:25%' fixed that, but I guess it's just a dirty hack.
b) Similarly, the 'Tweet' button for all the projects was slightly off center. Fixed that.
c) Finally, cleaned up the README: a few minor spelling mistakes, grammatical errors, and other misc. things were corrected. The 'Contributing' section was re-organized.