Use long form instead github due to non-https url (#496)

Author: ctran

README.rdoc

@@ -59,7 +59,7 @@ Into Gemfile from rubygems.org:
 
 Into Gemfile from Github:
 
- gem 'annotate', github: 'ctran/annotate_models', require: false
+ gem 'annotate', git: 'https://github.com/ctran/annotate_models.git', require: false
 
 Into environment gems from rubygems.org: