Add gitignore
Add install instructions
Improve code readability

Just minor changes, like:
* fix vertical indents (actually, I hate vertical alignment, but works here)
* change some $SHA variables to $sha - lower/camelcase is the standard
* added @throws phpdoc
* broke up some oneline ifs & foreaches
Make everything protected instead of private

There's no point in making it private; feel free to extend