Allow fully-yanked gems to be unyanked by the original owner

This still allows for a new user to swoop in and claim the gem by pushing their own version. Doing so would delete the previous ownership.
Refactor to yank a version directly rather than through its gem
Patch existing find_or_initialize_version_from_spec to make size an optional parameter.
size_in_kilobytes -> number_to_human_size
Change to cleaner syntax.
Add size to versions.
brought Chris's patch up to date and added a script to calculate sizes for existing gems
cleaned up Version#size interface
smoothed out size interfaces in Pusher and Rubygem
Update shoulda-context dependency to version 1.0.2
Update capybara dependency to version 1.1.4
Update newrelic_rpm dependency to version 3.5.4.33
Update connection_pool dependency to version 0.9.3
Update nokogiri dependency to version 1.5.6
Update timecop dependency to version 0.5.5
Update websocket dependency to version 1.0.6
Update librato-rails dependency to version 0.8.1
Update rewrelic_rpm dependency to version 3.5.4.34
Update timecop dependency to version 0.5.6
Update timecop dependency to version 0.5.7