add license information to gemspec
add license information to gemspec

this way it can be used with rubygems.org API

7091lapS/timecop,ducthanh/timecop,grosser/timecop,backupify/timecop,rednovalabs/timecop,backupify/timecop,ducthanh/timecop,grosser/timecop,travisjeffery/timecop,rednovalabs/timecop,7091lapS/timecop,kidaa/timecop