Upgrade to Bootstrap 3 SASS gem

* Remove bootstrap responsive include, that’s now the default
Update SASS variable names

* Switch from Bootstrap 2 camel cased variables to hyphen separated
Bootstrap 3 ones
* Update our own variables to match too
Update navbar to match bootstrap 3 markup

* Switch from brand to navbar-brand class
Update button classes to bootstrap 3

* Default buttons now need a btn-default class
* btn-mini is now btn-xs
Switch to using gem based bootstrap js

* Also upgrades all bootstrap js to the latest version
Update modal syntax to bootstrap 3

* Mostly adding new wrappers
* Visibility of modal is now managed using the aria attributes
* Move form onto one of the internal wrappers to maintain form aria role
Use a default vertical margin

* Use line height base and default font size
* Use in place of $line-height-base which is just a ratio
Update form class names to match bootstrap 3

* Use form-group, input-group and input-group-addon class names
Use the more verbose bootstrap 3 grid

* Extra wrapping is needed for constraining form elements to a width,
now that they behave like table cells
* This is the standard bootstrap grid way, but there’s no reason not to
improve on this later
Update breadcrumbs for bootstrap 3

* Ditch the custom divider in favour of bootstrap 3’s pseudo content
Keep traditional bootstrap 2 button styles

* For consistency with other apps, and for better affordances, use the
original button styles with gradients, rather than the flat versions
Fix pagination styles

* Avoid the blue active state on bootstrap 3’s default pagination styles
Update style guide copy for bootstrap 3

* Remove breadcrumbs section as they’re no longer custom
* Update grid examples
* Link to the correct bootstrap docs and code
Fix very short filter input in Firefox

* Rearrange order of wrappers, placing label in grid cell too and
removing form-group wrapper
* Convert filter from input to button for correct height, it seems
bootstrap 3 doesn’t like input type submit much,
http://stackoverflow.com/questions/18542343/is-there-a-way-a-aligning-my
-input-group-on-firefox-using-bootstrap-3
Use buttons not inputs

* Buttons have the correct height in Firefox when using bootstrap 3
Add margin to edit mapping tabs

* The tabs were too close to the top of the new form after the default
vertical spacing on forms was changed
Reduce default right margin

* Gutter widths are bigger now, and a spacing of 15px is too large
between buttons, reduce to 10px again.
Improve edit multiple modal layout

* Remove spurious extra spacing
* Demarcate footer region of modal again
Merge pull request #126 from alphagov/bootstrap-3

Upgrade to Bootstrap 3
Merge commit '376d07dd694add21382fdc26327830e679202b7a' into HEAD