Bump graph linelabel down by 30px

Adding margin-top to the linelabel moves it down the page, which
means it is included in the rectangle that screenshot-as-a-service
uses and so the image will no longer be clipped.
Make sure bundler is installed

Travis seems to have forgotten about installing bundler in our latest
builds, causing them to fail. We should probably just ensure it has
always been installed before we start trying to install gems. This
shouldn't affect the build if Travis decides to reinstate bundler.
Make rvm use 1.9.3

I've had a chat to the Travis guys in IRC and they suggested forcing rvm
into 1.9.3 to help fix this issue. They will be rolling out a fixed VM
later today.
Move colour bar out of breadcrumbs

When we have static pages in Spotlight, we'll want to include the colour
bar on pages where we don't have any breadcrumbs (eg the homepage).

This commit separates the two so they can be used independently.
Only display breadcrumb wrapper if crumbs exist
Move common configuration out of process_request

We'll need to reuse this configuration in all Spotlight pages, not
just pages that make use of process_request.
Add homepage

I've made a couple of changes while moving it across:

- Change link to blog and link text to be correct
- Remove live GOV.UK usage module (should be easy to re-add?)
- Add height and width to Transactions Explorer image, make it a link
Add Performance Platform labs page
Update PP Labs page with images, email etc
Add a 'mailto:' to an email address link
Allow array of arguments for axis config options.

This is to allow the "ticks" option to pass more than one argument if required.
Use UTC for D3 ticks, and start dates for ticks.

* Use start dates, not end dates, as axis tick labels: this is better logically,
  because if we are showing data from Jan 1st to Feb 1st, it is data for Jan,
  not Feb. Similarly, if we are showing data from Feb 1st to Feb 7th, it is data
  for the week of Feb 1st, not the week of Feb 7th. This has been okayed with
  design (Henry).
* Update availability collections to set timestamp to start_date, not end_date,
  because of the above change to use start dates everywhere.
* Use D3's native time intervals to set our axis ticks, and ensure we're using
  UTC D3 methods, to play nicely with our UTC tick formatting.
  * Update hourly graph to show ticks every six hours, rather than using four
    hard-coded ticks.
  * Update daily graph to show ticks on a Monday, to match the start dates
    for our data.
  * Ditto for weekly graphs.
  * Update monthly graph to use D3's native UTC month interval.
* Update tooltip formatting for quarterly graphs, as this was removed in
  previous commit.