Use Bootstrap table formatting for rounds

Just by adding some classes to the rounds tables, Bootstrap will add
borders, zebra striping, and active-row highlighting.
Switch to using `bootstrap-sass`

The gem `twitter-bootstrap-rails` provided an obsolete version of
bootstrap.
Use a FontAwesome check mark for couple marks.

It's a bit prettier, I guess.
Display a "recalled" heart for prelim rounds.

This required a fix to `Round#prelim_results`, since it was displaying
all couples with a certain number of marks, rather than just those in a
particular round.
Remove boilerplate from old bootstrap gem.

It no longer functions with the current version of bootstrap, so it must
be removed.
Color the recall heart green.

Because why not?
Add display of judges.
Add hidden text to mark/result cells for sorting
Separate classes for prelim and final tables

This makes it easier to select one or the other.
Clean up header class names.
Give couple rows a shared `couple_row` class.

Previously, there was only a `couple_<id>` class which was unique to
each row. Now, all rows have a shared `couple_row` class.
Add gem `jquery-datatables-rails`.

It has built-in support for filtering and ordering tables!
Prevent table cells from wrapping.

This keeps the table an acceptable height because the lead and follow
cells cannot wrap.
Add live filtering to (prelim) round tables

This uses the DataTables jQuery plugin to enable sorting and filtering.
It is incredibly easy and powerful. A great find!
Omit extra `th` in final rounds.

This messed up DataTables, since the table rows did not have the extra
column.
Narrow the filter box.

It was a bit wide.
`lodash-rails` gem and "floatThead" jQuery plugin

For floating the table header.
Add `floatThead` to float the header.

There is currently an annoying 6px gap between the top of the floated
header and the top of the viewport. I've reported this on both
floatThead and jquery-datatables-rails:

  - https://github.com/mkoryak/floatThead/issues/35
  - https://github.com/rweng/jquery-datatables-rails/issues/85

Hopefully this gets fixed somehow.
Merge branch 'results-live-filter' into develop