Remove unusued variable
Update release date
Install PEM files when installing RubyGems

Due to an oversight, only .rb files were installed when rubygems was
installed.

The .pem files necessary for HTTPS connections were ignored.  This,
combined with a separate bug from @872ab85 may prevent users without any
SSL certificates from installing gems or updating RubyGems to a fixed
version.

Now .pem files are installed along with .rb files.

Fixes #491