Add the ability to validate the X-Hub-Signature header
Merge branch 'validate_x_hub_sig' of https://github.com/Phillipmartin/jekyll-hook into Phillipmartin-validate_x_hub_sig
Addressed comment in #12
Merge pull request #20 from developmentseed/Phillipmartin-validate_x_hub_sig

Phillipmartin validate x hub sig