Update devDependencies.
Cleanup sinon spies and stubs and do not allow call through when using proxyquire.

Allowing proxyquire to call through messes up with the coverage. Regargin cleaning up sinon, it is better not to overwrite functions and forget to reset it later…
Warn about ghooks not being installed and bail.

Had to wrap the entire hook template into an IIFE so that esprima stop complaining about 'return'ing not being in a function body.
Addresses #9.