Issue #7: Capturing the first parameter to the install script to tell it a new hook was installed.

After a new hook is installed, they will "dial back" to git-guppy/scripts/install. Given that
the gulp execution is async, the git-guppy/scripts/install was reading the App's package.json
before it was updated. In order to overcome this, the install script will simply call
git-guppy/scripts/install "hook-name", adding the "hook-name" to the list of "hooks" to be
installed.

*	modified:   scripts/install.js
- Capturing the command line argument that's the name of the hook just installed.
- Adding it to the list of hooks
- The rest is history :)
Issue #7: Fixing the path to finding the package.json of the app executing.

After the script installation, the path to the APP's package.json can be
computed with the current directory running gulp or git.

*	modified:   lib/hook-collector.js
- Using the process.env.PWD value to compute the location of the package.json
  of the running app.