Partially revert "Add IP check against DNSBLs at account sign-up"

This partially reverts 6a5cd3ca - we keep the migration and add a new
migration that reverts it in order to keep migration history intact.

See merge request !2643

Prevent transient Capybara timeouts during feature tests

The problem occurred because asset compilation takes a long time, so
when the asset cache didn't exist and the first test ran, it would often
(randomly) time out during the generation before the actual test even
had a chance to run.

Now we check if the cache exists before the suite runs, and if not, we
manually fire a request to the root URL in order to generate it. This
should allow subsequent tests to use the cached assets.

See merge request !2646

Revert "Revert "Remove the `:coffee` and `:coffeescript` Haml filters""

This reverts commit b0145d765b94d2cef86b10b6dd22895779cfef33.

See merge request !2642

fix syntax error on 2.1 and rubocop on 2.2

Background:

Hashes `{:'key': 'value'}` are not valid in 2.1 but are recommended by Rubocop on 2.2. We only use those when we have a key such as `weird-key`, `weird.key`, etc... 

We could disable Rubocop but it wouldn't warn us about the recommended syntax since `Ruby 1.9`: `{key: 'value'}`, which is valid for `Ruby 1.9+`.

Workaround 1 could be disabling `Style/HashSyntax:` in `rubocop.yml`. 

Workaround 2 (tried in this MR) is to trick Rubocop using `.to_sym` which is effectively the same as adding the `:`. This would allow to keep the warning in place.

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/12801

See merge request !2637

The problem occurred because asset compilation takes a long time, so
when the asset cache didn't exist and the first test ran, it would often
(randomly) time out during the generation before the actual test even
had a chance to run.

Now we check if the cache exists before the suite runs, and if not, we
manually fire a request to the root URL in order to generate it. This
should allow subsequent tests to use the cached assets.

This partially reverts 6a5cd3ca - we keep the migration and add a new
migration that reverts it in order to keep migration history intact.