Update spec name and some attributes
Add some rules
Add wkhtmltopdf 0.12.0 for linux i386 and amd64
Add wkhtmltopdf 0.12.1-fef236e for Mac OS X
Add dispatch script
Change version to 0.12.0
Modify gem name and description
Remove _gem suffix
Add helper method to get dispatch script path
Change return value type to String
Add 'Use with wicked_pdf' section
Merge branch 'develop'