New and improved chef-mod_security

 * Updated to mod_security 2.7.7 and OWASP CRS 2.2.8
 * Downloading source and CRS tarballs from SpiderLabs GitHub releases
 * Added SHA256 verification of downloaded source and CRS tarballs
 * Downloading tarballs to Chef file cache path instead of under the mod_security dir
 * Added integration testing using test-kitchen across multiple platforms
 * Foodcritic and Rubocop fixes

Fixes issue #1. modsecurity_crs_35_bad_robots and modsecurity_crs_50_outbound now ship with two datafiles per rule. data_filenames to link is now an array that is iterated over rather than a string.

(Rebased my develop branch and squashed into fewer more relevant commits)