[WIP] Update gitlab and gitlab-shell repos in Makefile

AFAIK, currently there is no reference how to update the source files of `gitlab` and `gitlab-shell`. I gave this a brief test and it works. If anyone can also test this it would be cool. If we decide to merge it, a section in README will be added as well.

See merge request !23

Add g++ dependency to ubuntu install.

Required to build unf_ext gem.

See merge request !22

Sed works well for global search and replace, but if you only want to
change one occurence it seems to be easier to use ed.

Fix gitlab-shell redis socket config

Right now socket option is not commented in example config. See https://gitlab.com/gitlab-org/gitlab-shell/blob/master/config.yml.example#L34. This cause gitlab-shell use default socket config which is invalid

See merge request !19

Arch Linux pre-installation instructions

See merge request !18

Clone this repo

I was confused where to run `make` command because it was no `clone` instructions for this repository.

This MR add section with 2 commands: clone repo and cd into it. I think it will be more user-friendly

See merge request !17

pkg-config and cmake dependency for OSX

OSX also needs `pkg-config` and `cmake` dependency. It's not installed per default.

See merge request !16

Readme improve

The post-installation part was not looking correctly and was written in spoken tone. This should fix it.

See merge request !15

Markdown code blocks apparently need 4 spaces; 3 is not enough.

Fixes #11.

We were describing post-install development setup steps in the README
that were also in the post-install message. This commit removes the
instructions from the README in favor of the post-install message.

Connect to Redis via sockets only

See merge request !14

This is now supported on master by gitlabhq

Requirements clear in readme

See merge request !13

Add Ubuntu Requirements to README

Added the apt-get install step for Ubuntu to the Requirements section of the README

Also moved the ruby and bundler hints up in order to apply to all install types.

Issue #7

See merge request !12

Use Postgres bin path

Postgres on Ubuntu doesn't include the initdb and postgres commands on the PATH, but are still available from the postgres bin directory.

Updated the Makefile to use pg_config to find the postgres bin directory, and use it for the initdb command, and for the postgres command in the procfile

Works towards completing issue #7

See merge request !9

Add to git ignore

**What does this MR do?**

It adds the `.bundle` directory to the gitignore

**Why is this MR needed?**

Otherwise after you run `make` it will say that your git repo has changes. But it does not really, since that directory should not be commited.

See merge request !10

Signed-off-by: Jeroen van Baarsen <jeroenvanbaarsen@gmail.com>