update the link to holidays
Explicitly require HTTPS rubygems source

Require HTTPS rubygems.org to reduce the risk of MITM attacks
Improved docu, added BusinessTime::Config.work_hours example.
commiting gemfile.lock change from months ago when I released
Merge branch 'master' of github.com:bokmann/business_time
Merge pull request #29 from juliendsv/update_readme_broken_link

Update the broken link in the Readme
Merge pull request #30 from chapmajs/patch-1

Explicitly require HTTPS rubygems source
Merge pull request #31 from martini/master

Improved docu, added BusinessTime::Config.work_hours example.