Add option to update gitlab-workhorse

Already tested on my kit :)

See merge request !91

Stash any uncommitted changes before pulling



See merge request !83

Fedora in install instructions



See merge request !85

Install dependencies from package

Some more improvements to the Vagrantfile and documentation.

* Install RVM from their PPA
* Install Recent Go from Ubuntu-LXC PPA

See merge request !90

Disable NFS on OS X and Fix issue with initdb

Syncing GDK folder using rsync instead of vagrant default share, will fix #46.

Disabling NFS on OS X will make sure we don't have incorrect UID/GID on guest machine, as described on #68.

See merge request !89

Recent Go is published from the Ubuntu LXC PPA
RVM PPA is from official contributor

Update README to include bundle install for dev kit itself

Currently the `README` doesn't mention the fact that you need to run `bundle install` on the dev kit to get foreman etc.

WRT markdown style guide - I've gone for the 80 char width option because I write python usually  There already seems to be a mixture in this file, so I guess thats not too important so long as it renders correctly?

See merge request !87

Elaborate on post-installation instructions

To ensure there is clarity in the user's mind concerning what processes they are setting up and what ports they can expect to find a service.

See merge request !82

Fix-up items missed by !79 for #63

I forgot to search and replace the old section "Install Gems and Repositories" mentions in the other sections in the previous MR.

See merge request !80

Improve clarity of the importance of certain GDK instructions

This change draws better attention to the necessary `make` command within the gitlab-development-kit by moving it up one markdown title level. I feel this is a necessary move because the previous section is essentially a list of platform choices, hence the reader will be intentionally skimming/skipping and could easily gloss over this important section.

See merge request !79

Add a troubleshooting section for eventmachine gem compilation.



See merge request !78

Add missing forwarded headers in nginx configuration

This is in order to have the same headers in dev as recommended for GitLab deployment.

See merge request !77