adding helpers option to assemble options that allow providing a glob pattern to add a list of helpers
updating engine tests to add an additional test to cover files and glob patterns
updating to use the process cwd if the cwd is not set and adding tests to the Gruntfile.js that use the custom helpers
fixing helper loading to allow providing a register function in your helpers and take in the actual handlebars engine
making sure there's an underlying engine provided in the plugin, otherwise pass the plugin itself
Merge pull request #189 from doowb/master

Adding ability to load helpers through a glob pattern.