Add support for zip archives.

Additionally, this adds support for bz2 compression and uncompressed tar
files.

Any unknown format falls back to tar.gz.
Update Gemfile.lock

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Merge pull request #20 from jhollingsworth/feature/zip-archive

Add support for zip archives.
Fix comment to Gitlab::Git::Repository.new in README
Allow to specify diff paths
Add support for raw blob search

For issue:
http://feedback.gitlab.com/forums/176466-general/suggestions/4566001-expose-raw-object-search-via-the-gitlab-api
Merge pull request #21 from tgerdes/raw_blobs

Add support for raw blob search
Version to 4.0.0. Updated CHANGELOG

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Merge pull request #19 from skv-headless/master

Allow to specify diff paths
Add compare docs to readme

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Version 4.1.0.pre

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>