move eventmachine gem to development dependency.
load version.rb from .gemspec.
modernize Gemfile syntax.
remove version string replacement at updating .gemspec.
Add missing test files in the gemspec.

Once sinatra-contrib was packed as a gem, some rspec tests failed
because of missing files in the gemspecs.
Merge pull request #108 from GuillaumeBouteille/fix-missing-gemspec-files

Add missing test files in the gemspec.
Merge pull request #93 from unakatsuo/fix-gemspec

Fix Gemfile & .gemspec
update Gemfile.locks
get rid of stdlib warning
update authors