Update README.md

Minor typo fix
Merge pull request #10 from maxcanna/patch-1

README.md typo
better readme
yml instead of yaml
correct license name in composer.json file
minimum stability stable, and updated deps
new travis build status badge
new php version and new symfony versions
some sensio labs insight fixes
sensio labs insight badge
removed native checker
Merge branch 'feature/remove_native_checker' into develop