Fixes save button in footer

Fixes #30
Adds margin to bottom of form

Floating save button was covering up bottom of form, so this adds a
margin to offset the save buttons height.
Moves existing categories inside categories box

Categories box was above categories section, this moves it into the
category box.
Removes existing categories sections
Merges `master`
Fixes typo in CSS

SASS was missing a curly bracket, this fixes that.
Re-adds slugs logic

slugs variable was accidentally removed when removing existing
categories section. This variable is needed in the categories form
partial, so this commit re-adds it.
Removes reference to existing categories from test

Test was looking for existing categories box, but it is no longer
present. This commit removes that reference.
Re-adds existing categories

Tests depended on the existing categories DOM, this re-adds them.
Adds location name to floating footer

- Adds "Editing" location name to floating footer, next to the save
button.
- Replaces "and" with ampersand to save space in save button.
Remove excess margin
Merge pull request #41 from codeforamerica/style-updates

Style updates