Add capybara-screenshot gem

This is a handy little gem that automatically saves the page and a screenshot when a Capybara test fails to `tmp/capybara/` so you can easily see why it might have failed without adding your own `save_and_open_page` directive in the code.

Also reduces the timeout for Capybara tests when not in a CI environment.

See merge request !578

Get Gitorious importer to work again.

Fixes #1504.

See merge request !576

Use Projects::CreateService to fork projects so that after-create hooks are run.

Makes for cleaner code and less duplication, and causes the "User created project Namespace / Project" event to be posted and system hooks to be run.

See merge request !575

Minor design change grab-bag 🎉

I started with one simple change and found a few more, so here they are.

### Simplify icon style selectors

All FontAwesome icons have an `fa` class, so just use that.

### Don't override color of code blocks in notes

This was a pet peeve of mine.

| Before | After |
|:------:|:-----:|
| ![Screen_Shot_2015-04-23_at_4.14.23_PM](https://gitlab.com/gitlab-org/gitlab-ce/uploads/c77cb0816bf0f05cb8c4105cdd8b3ec6/Screen_Shot_2015-04-23_at_4.14.23_PM.png) | ![Screen_Shot_2015-04-23_at_4.15.44_PM](https://gitlab.com/gitlab-org/gitlab-ce/uploads/463c1d2052e12444563f5e2c102ac51e/Screen_Shot_2015-04-23_at_4.15.44_PM.png) |

### Items with tooltips don't need a 'data-original-title' attribute

This attribute gets added dynamically by Bootstrap's tooltip JS based on the `title` attribute

### Fix Profile > Design live-updating

`ui_blue` wasn't added to the list of classes to remove, so if a user changed to that theme, any subsequent changes wouldn't be live-updated.

This change refactors Gitlab::Theme a bit to make it harder for this to happen in the future with new themes.

### Remove the `has_bottom_tooltip` class

Bootstrap's tooltip JS can read the placement from a `data-placement` attribute.

Further, when we supply the `selector` option to `tooltip`, tooltips will be added to any dynamically-added elements matching the selector, without us having to re-call the `tooltip` method.

See merge request !569

Also adds capybara-screenshot, which will automatically save the page as
html and an image whenever a feature fails. Handy for debugging.

[ci skip]

Refactor ReferenceExtractor

See merge request !557

When collapsed it's on the right like everything else, when expanded
it's on the bottom.

Also matches CommitReferenceFilter's new behavior of always using short
SHAs in the link text.

Now when a user pastes a full SHA like
`d7f61aff`, its link text will only show
`d7f61aff` for brevity.

Bootstrap's tooltip JS can read the placement from a `data-placement`
attribute.

Further, when we supply the `selector` option to `tooltip`, tooltips
will be added to any dynamically-added elements matching the selector,
without us having to re-call the `tooltip` method.

`ui_blue` wasn't added to the list of classes to remove, so if a user
changed to that theme, any subsequent changes wouldn't be live-updated.

This change refactors Gitlab::Theme a bit to make it harder for this to
happen in the future with new themes.

Bootstrap's tooltip JS just uses the `title` attribute.