Move the bulk of the raygun logic out of the bin and into the lib.
Download the app protoype from github instead of embedding it.

- Fetch the latest tag from carbonfive/raygun-rails4.
- Check to see if the tarball is already cached under ~/.raygun.
- Download if it's not cached.
- Check that the raygun gem is new enough for the protoype.
- Generate the new app using the newest tarball.
Remove the prototype, it's now in its own repo.
Switch from 'bundle update' to 'bundle' because it's safer.

We want to increase the likelihood of success on that first run through. 'bundle' will use the same gems that have passed on CI, so they should work for the user too.
TODO is old and not really relevant anymore.
Update changelog.
Don't need the cleanup script anymore.
Update readme to reflect how raygun finds its application prototype.
Merge pull request #112 from carbonfive/issues/split-raygun-and-prototype-112

Separate raygun executable from application prototype