Use NGINX for HTTPS development

Fixes https://gitlab.com/gitlab-org/gitlab-development-kit/issues/129

Stunnel is not enough for proper HTTPS development so I brought back our old NGINX configuration.

See merge request !158

Use 'exec' for clean stunnel shutdown

Closes https://gitlab.com/gitlab-org/gitlab-development-kit/issues/128

Missing 'exec' caused Foreman not to terminate stunnel when shutting down.

See merge request !157

Document how to enable Spring

Needs https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/4752

Closes https://gitlab.com/gitlab-org/gitlab-development-kit/issues/127

See merge request !156

Set up GDK with a gitlab-ce fork by default



See merge request !155

Make host also customizable with file/environment variable

Since we have the `port` value configurable I think it'll be good to add such configuration options also for the `host` value. For example I'm running GDK inside of docker container and I need to bind gitlab-workhorse to container's external address, not the container's `localhost`. I could set this manually in the `Procfile` but this will be easier and faster with environment variable and also this will be consistent with the `port` value configuration method.

See merge request !151

Add instructions to generate a license for GitLab EE



See merge request !153

- Add instructions to generate a license for GitLab EE

Fix GitLab logo display for certain shells

Backslash escapes are disabled in `echo` by default in most linux distributions I've seen. Man page for current Fedora echo:
```
       -e     enable interpretation of backslash escapes

       -E     disable interpretation of backslash escapes (default)
``` 

This MR explicitly enables escapes. Screenshots before and after  :

![gl_picture_before](/uploads/17abeaa4671da38ee7e172a5a7477678/gl_picture_before.png)
![gl_picture_after](/uploads/7aa229f1913a8340395196fea099ff78/gl_picture_after.png)



See merge request !152

Added CLI tanuki 

CLI tanuki, to dramatically improve productivity through cuteness.

**Would love to see some improvements of this.** *After the higher priority issues* 

![Screen_Shot_2016-05-17_at_00.45.44](/uploads/3405ed77b4b4ec8d017c8cb6632491c7/Screen_Shot_2016-05-17_at_00.45.44.png)

See merge request !150

InfluxDB and Grafana

Closes https://gitlab.com/gitlab-org/gitlab-development-kit/issues/119

See merge request !149