Remove hack for load_yaml

This commit complies with comment to remove after the 1.5 release of
RubyGems.
Merge pull request #815 from zzak/remove_load_yaml_hack

Remove hack for load_yaml
Add #815 to History
Fix "coding:" detection for release notes

The regular expression used would capture the first "=" of the first
history entry which contained the latest release notes.  This has been
corrected to not consume anything beyond the header text.

Fixes #814
Adding CONTRIBUTING file.

There is some info on the [RubyGems Site][1] that wasn't easy to find in
this repo. In an effort to make it easier for others to start contributing, as
well as taking advantage of a nice [CONTRIBUTING FILE SUPPORT][2] on Github I'm
copying that information here for people thinking of contributing to RubyGems.

[1]: http://guides.rubygems.org/contributing/
[2]: https://github.com/blog/1184-contributing-guidelines
Merge pull request #849 from amerine/contributing

Adding CONTRIBUTING file.