* build-essential requires make, gcc
* remove libmysql++-dev: the mysql2 gem only requires libmysqlclient-dev
* remove postgresql-server-dev-9.1: the pg gem only requires libpq-dev
* replace python-dev, python-pip with python2.7: the pygments.rb gem only requires python2.7

Fixed a typo.

Also updated status task and installation instuctions.

Update docs for PostgreSQL installation

The config skeleton for postgres is called `database.yml.postgresql`,
not `database.yml.postgres`.

Git Smart HTTP protocol runs on `gitlab:gitlab`.

Added documentation for getting project hook and editing project hook.