Fix commit author email for bitbucket

Fixes #602.
Email is parsed from raw_author field in bitbucket post-commit hook. It's whatever user has in `git config user.email`. 
I could also check if the value provided is valid email and in case it's not - fallback to whole `raw_author` field or just `author` as it is now. I'm not sure it's necessary, though.

Any comments appreciated.
Just to be safe, we should check to ensure the substring match has > 0 items in the array. Although it is unlikely it would prevent a potential panic in the code.

If the substring match is not > 0 we could just use the RawAuthor value