Fixing bad metadata structure
Merge branch 'master' of github.com:Modernizr/Modernizr

* 'master' of github.com:Modernizr/Modernizr:
  Corrected metadata typo in `cssmask` detect
  Updating syntax.
  Adding documentation for API.
  Adding tests for programmatic API.
  Remove exit, it can cause upstream processes to bail too soon.
  Simplify context issue by first setting a new cwd, then requiring grunt. This scopes grunt to the Modernizr directory and avoids manipulating upstream context.
  For interoperability purposes, have the build API explicitly declare a current working directory. Revert to previous cwd on exit.
  Adding a build api.