Fixed some links

* Added Google group to FAQ on docs
* Changed IRC link
* Fixed link to contributing broken by 326faec
Build from Dockerfile on stdin requires a hypen
There is a missing hypen in the documentation:
    `docker build < Dockerfile` will complain
    `docker build - < Dockerfile` will not complain
Merge pull request #855 from samjsharpe/fix_missing_hyphen

Build from Dockerfile on stdin requires a hyphen
Fixed broken link in README
Merge pull request #867 from Turbo87/patch-1

Fixed broken link in README
Support for special namespace 'src' (highland support)
Escape remote names on repo push/pull
Merge pull request #814 from dotcloud/708-pushpull-multislash

Support for special namespace 'src' (highland support)
Merge pull request #840 from dhrp/just-fixed-some-links

Fixed some links. Closes #839 #838 #835