Merge branch 'ci-config-docker-support' into 'master'

Adjust CI config to support Docker executors

A shell script (based on the one for GitLab CE) has been added to
support Docker executors. Tags have been added to make sure builds are
only executed on appropriate runners.

This makes it possible to test forks of the GitLab CI repository on
public runners. Previously, builds failed with the following error:

```
$ bundle --without postgres
/builds/eldamir/gitlab-ci.sh: line 29: bundle: command not found

ERROR: Build failed with: exit code 127
```

See merge request !212

.gitlab-ci.yml

 before_script:
-  - export PATH=~/bin:/usr/local/bin:/usr/bin:/bin
+  - ./script/prepare_build.sh
   - ruby -v
   - gem install bundler
-  - cp config/database.yml.mysql config/database.yml
   - cp config/application.yml.example config/application.yml
   - cp config/secrets.yml.example config/secrets.yml
-  - 'sed "s/username\:.*$/username\: runner/" -i config/database.yml'
-  - 'sed "s/password\:.*$/password\: ''password''/" -i config/database.yml'
   - bundle --without postgres
   - RAILS_ENV=test bundle exec rake db:setup
 specs:
   script: SIMPLECOV=true RAILS_ENV=test bundle exec rake spec
+  tags:
+    - ruby
+    - mysql
 rubocop:
   script: bundle exec rubocop
+  tags:
+    - ruby
+    - mysql
 brakeman:
-  script: bundle exec brakeman
\ No newline at end of file
+  script: bundle exec brakeman
+  tags:
+    - ruby
+    - mysql

script/prepare_build.sh

+#!/bin/bash
+if [ -f /.dockerinit ]; then
+    export FLAGS=(--deployment --path /cache)
+
+    apt-get update -qq
+    apt-get install -y -qq nodejs
+
+    wget -q http://ftp.de.debian.org/debian/pool/main/p/phantomjs/phantomjs_1.9.0-1+b1_amd64.deb
+    dpkg -i phantomjs_1.9.0-1+b1_amd64.deb
+
+    cp config/database.yml.mysql config/database.yml
+    sed -i "s/username:.*/username: root/g" config/database.yml
+    sed -i "s/password:.*/password:/g" config/database.yml
+    sed -i "s/# socket:.*/host: mysql/g" config/database.yml
+else
+    export PATH=$HOME/bin:/usr/local/bin:/usr/bin:/bin
+
+    cp config/database.yml.mysql config/database.yml
+    sed -i "s/username\:.*$/username\: runner/" config/database.yml
+    sed -i "s/password\:.*$/password\: 'password'/" config/database.yml
+fi