docs(errorcode.md): add the EcodeRootROnly error
Add PHP library.

We implement the api client useing php.
Merge pull request #612 from congpeijun/master

Add PHP library.
Merge pull request #607 from Asmod4n/patch-1

Added Error 107 to Documentation
docs(CONTRIBUTING): add code style section
Merge pull request #613 from unihorn/29

docs(CONTRIBUTING): add code style section
fix(CONTRIBUTING): minor grammar fixes
Merge branch 'master' of github.com:coreos/etcd