Added Refund ability.

- I added the refund ability for admins only, to see.  The link appears
  next to the list of already taken categories on that event.
- I cleaned up some of the unused instance variables.
Cleanup.
OCD.
Functionality for discounts:

- Added the base classes and a lot of logic for how discounting a vendor will work on the back-end.
Now just need to tie it into a form and finalize it in the morning.

Note to self: Great deal of headaches will come when I want to allow for global discounts based on
all events for 1 category.  To alleviate this make sure I set a VendorPricingTier model not tied into
active record so that we can do quick (KEY: QUICK) on a hash table for some of the more important info.
A library file is fine for now based on all testing, but for later usage abstract this out into a global class.
Updated the discount actions for Form.

- Added the database column in a more appropriate manner.
- Updated the logic for pretty fields on the front-end.
- Also updated some of the javascript to smooth out the form actions,
  and passed in the state variable to handle multiple states.

Next to do:
- If cat_event_user has been set by admin for discount do NOT show it in
  the taken categories until that user has accepted that discount and
  hit that category on their form.
- Show the user that logs in with discount that admin has applied that
  there is a discount available for them to use.
- Once a user hits submit and accepts and PAYS for that booth under
  discount then call that discount 'taken' on the form.  Double check
  this workflow on production.
CatEventUsers update to discounts on the show page

- Now discounts carry through from an admin creating one, to a user
  going to a page seeing they have said discount that admin created and
  then clicking purchase the amount carries through using discount tier
  calculation.

Bug that I noticed:
- Discounts are not working for a user if the user logs in with Google.
  An admin can set said discount but for some reason the app is not
  recognizing the discount when the user logs in.  Even though we are
  looking it up via
  CatEventUser.find_by_user_id(current_user.id).discount(tier)

Explore this further.
Added Sorting Plugin and Implemented Sorting

- I added the jquery.tableSorter.js plugin from a trusted source.
- I added the tablseSorter to the views it belongs to (vendor and
  lighthouse_user)