Add BundleCheck pre-commit hook

Add a hook that checks that a `Gemfile.lock` matches the given
`Gemfile`/gemspec, similar to the `PostCheckout` `BundleCheck` hook.
They are meant to compliment each other.

Change-Id: I34e9cbcc58bb873d20a74bfa62b25ff1671bbe95
Reviewed-on: http://gerrit.causes.com/35608
Reviewed-by: Shane da Silva <shane@causes.com>
Tested-by: Shane da Silva <shane@causes.com>
Disable IfUnlessModifier in Rubocop config

This is really noisy and not that useful, especially when the one-line
body of the if/unless is very long.

Change-Id: Iaed16dfb0e8c89997784b5b7c1b15ec0e2e9f8f8
Reviewed-on: http://gerrit.causes.com/35609
Reviewed-by: Shane da Silva <shane@causes.com>
Tested-by: Shane da Silva <shane@causes.com>