Updated source in Gemfile

:rubygems is deprecated as of Bundler 1.2.4
Also test on ruby-head
Allows failures on 2.0.0 and ruby-head
Added Gemnasium badge to the README
Fixed class-method call in SteamId initializer
Merge pull request #9 from elitak/class_method_fix2

Fixed class-method call in SteamId initializer
Added Eric Litak to contributors
Strip the Web API key from debug output
Adapted GameItem parsing to DotA2 API changes
Added configuration for Coveralls
Added Coveralls badge to README
Fixed require order in test/helper.rb
Added license to gemspec
Updated license year
Version bump to 1.3.5
Merge branch '1.3-stable'