Adds category search to homepage

Adds initial category search infrastructure to the home page. Note that
category search icon is temporary.
Styles category/keyword swapper

Changes icon of category swapper and changes styles so the icon is not
included on inside pages.
Updates 'no results' category styles

Updates category styles on 'no results' page to match category search
box size.
Updates category search styles

The category search clickable area was the whole top area of the seach
form. This commit makes it so it's just the search type button in the
upper-right of the search form. It also edits the styles, which makes
the button a bit larger.
Fixes #209 - clears input fields on click

When input textfields have focus, this commit adds the functionality to
clear the value from the fields.
Adds web storage for remembering search type selection

Sets the default search view to the category search and adds web
storage for remembering last search view selected. Also performs
styling tweaks.
Updates rollover border styles for categories search
Adds category seach styles for mobile screen sizes

Category search was not optimized for mobile viewing. This adds styles
to the smaller screen size media query.
Merge pull request #213 from codeforamerica/category-search

Category search