Update README.md
Support Rails 4.1.2
Merge pull request #573 from jgadbois/rails4

Support Rails 4.1.2
Remove errant backtick

Fixes #575
Remove non-working example links from bottom of Readme
Merge pull request #579 from tomhanlon/rails4

Remove non-working example links from bottom of Readme
Redirect posts#show to topics#show

Fixes #576
Bump to Rails 4.1.4

Fixes #580
NilUser inherits from Forem.user_class

Topic#set_first_post_user expects Forem.user_class