Bump the frontend toolkit from 0.12.6 to 0.46.0

This might look like a big jump in version numbers but the diff
isn't that huge.

https://github.com/alphagov/govuk_frontend_toolkit/compare/ef84748...44d129d
Set $path correctly in Sass

This points to the base directory where Sass should look for images.
Remove separator.png from assets directory

This is already copied over into the public directory from the
govuk_template, so it's just duplicated here for no good reason.
Use file-path mixin for our own assets

This doesn't give us cachebusting, but it's a nice enough solution
for the time being.
Remove NTA Tabular Numbers in header/footer links

Chrome on Windows doesn't link it.

https://code.google.com/p/chromium/issues/detail?id=344347
Merge pull request #314 from alphagov/bugfix-remove-tabular-numbers-from-header-links

Remove NTA Tabular Numbers in header/footer links
Remove "costs" & "other notes" fields from stubs.

These will only be useful when we have Transaction Explorer data
about costs on the dashboards. At the moment, there's no data
about costs being shown - so these are superfluous.

Remove them from Stagecraft stubs.
Update development dependencies

I don't think there's anything in here we need to be too
concerned by.
Remove redundant lint-branch task

There's no lint on master, so if you've introduced lint it is
by definition on your branch.
Update documentation
Merge pull request #313 from alphagov/compile-sass-image-paths-correctly

Compile Sass image paths correctly
Merge pull request #317 from alphagov/update-dependencies

Update development dependencies
Automatically give modules a class of their module type

These were being hard coded in lots of places. Simplify by automatically adding the module type as a className to all modules.
Also allows all modules to get extra classNames from config.
Return `data` property of input to Collection#parse by default

99% of instances of backdrop output are in format { data: [...] }
Set default parse method to reflect this
Set passed `queryParams` object to collection by default
Added number magnitude option to formatters
Allow classNames from config to be strings as well as arrays
Implemented KPI modules
Removed trailing spaces.
Tests to cover magnitude formatters.