Move "config.yml" to "_config.yml"

As in docs it is mentioned that Crotal save configuration in
"_config.yml". Also keep it consistence with Octopress.
Show success message after creating new post.
Changed variable "_config.yml" => "_config_yml"
Create git repo in site directory.

This creates an empty git repo in specified site directory and
create `source' branch (`source' branch would keep only raw files/
scaffolding/config files). Add all inited files under `source' branch
and commit them.
Added dependency
Create & commit empty branch "master", will use it later.
Add `.gitignore' file in initiated repository.
Added `.gitignore' file as part of scaffolding.
add _sites
using `_sites' as publish dir, as per docs.
Enabling git deployment method.

Major changes:
While initiating crotal site using `crotal init site_name`, this patch
creates two branches; source and master. `source' holds raw data that
needed to generate blog, i.e markdown files, config file, etc. And
master branch would hold final generated files by crotal those are ready
to deploy on `github'.

So when you `deploy' your site with `deploy_default' = "git" it switches
to "master" branch and copy processed file from PUBLISH_DIR to BASE_DIR and
push changes to remote github repository.
Skip temporary, garbage file generated while editing blog.