Add .ruby-version to 1.9.3

We don't actually execute any Ruby in this project, except for during
the build process.

I think this will alleviate some issues when installing gems:

    sudo: no tty present and no askpass program specified
    Sorry, try again.

    Gem::Exception: Cannot load gem at [/var/lib/gems/1.9.1/cache/sass-3.2.12.gem]
Use bundle exec when building Sass in production

So that we use the copy of the sass binary in vendor/cache.
Use tabular numbers in more info links
Check in first version of monthly-by-lot timeseries graph
Use only one year's data in Backdrop stub, like live query
Add basic test for g-cloud by-lot graph
Use tabular numbers in graph callout
Use pluralise() method in volumetrics/number view

Corrects "last 1 weeks" -> "last 1 week". Which still sounds awkward,
but is at least a little better.
Update README and CONTRIBUTING
Sort controller_map alphabetically

This does not modify any behaviour.
Sort package.json dependencies alphabetically
Update grunt and grunt-contrib dependencies
Merge pull request #114 from alphagov/use-tabular-numbers

Use tabular numbers in more info links
Merge pull request #117 from alphagov/end-of-year-tidy

End of year tidy
Change formatDuration method to use a given unit

Previously we relied on the visual length (number of characters) of
a string to determine what unit it was output as. I think we should
be able to specify the unit (milliseconds or seconds) in the method
signature.

Allows formatting to a given number of significant figures.
Merge pull request #118 from alphagov/58790312-page-load-time-seconds

Display page load time in seconds
Fix neg number bug in roundToSignificantFigures

And make it a method on View.
Move rounding changes tests into correct place

And remove one duplicate.

And tidy whitespace on an object, remove unused thresholds (they're
duplicated below).
Change rounding thresholds from 500 to 1000

For all orders of magnitude.

I think there's an opportunity for some refactoring here.
Fix asset digest in development

I broke Sass compilation in development. Sorry.

Currently, development will use a cachebusted URL for CSS. However
when you make a change to a Sass file, Sass will only create a file
called spotlight.css which means you won't see the changes you've
just made (as your view is still using the old cachebusted file).

This change means that in development, the asset digest is still
used but the cachebusted filename is equal to the non-cachebusted
filename. So you can go and edit Sass files to your heart's content
and see the changes without restarting the server.

Happy New Year! :fireworks: