Avoid DOM parentNode traversal (after init, `aria-controls` attribute can be used instead).

This reduces the radios we are trying to hide the
content for to only be those which are controls.

This covers the following use cases:

1. If the control sent in is not a control

All content controlled by radios in this group
will be hidden.

2. If the control sent in is a control

All content controlled by radios in this group
will be hidden and the content for the control
will be shown.

The following errors came up:

- 80:54: Block must not be padded by blank lines.
- 105:12: Closing curly brace does not appear on
  the same line as the subsequent block.

They were rewritten to point at a local version of
jasmine-core but this is not listed in our
package.json so only exists in /node_modules as a
dependency of grunt-contrib-jasmine.

At the moment the ShowHideContent module binds
events to all radios and checkboxes in
block-labels. This mean a user clicking on any
block-label in the page will trigger code to
show/hide its related content, even if there is
none.

This commit limits the block-labels that trigger
the code to show/hide content related to it to
those that have that relationship.

The `result` variable will always be a string
(rather than an expression) so doesn't need
parenthesis.