Execute command directly without using shell

More detailed warning about symlinks in repos_path

   use Shellwords.shellwords for splitting origin_cmd instead of .split(' ')

When that branch contain a '/' in the branch name.
Fix for git over ssh

Fix typos

The syntax for `sed -i` is incompatible between GNU sed and
BSD sed. By Tempfile from the Ruby standard library we can
avoid using the `-i` option of sed.

Support adding and removing branches and tags

Update config.yml.example for grammar

The previous commit has the code addition to support adding and removing branches and
tags in a repository - This commit ensures basic test cases are supported.

This commit adds support to create and remove branches and tags from gitlab-shell.

The code style was followed as closely as possible to the original.

The purpose of this commit is that I will be adding support to the Gitlabhq (Gitlab) project
in order to allow adding and removing of branches and tags through their API.

Logger

added optional argument so to override default repo location

propably better ssh-key id finding in ARGV

Add ca_file/ca_path configuration options.