Added shifts table, model and seeder
Added function to retrieve shifts for a TA for a certain period of time
Modified Seeder to display better test cases
Added TA view of shifts. Minor correction to constructors. Added route to shifts.
Made the link a little bit cleaner
Made navigation between weeks bigger
Modified shifts to display as one block. Added option to drop a shift. Dropped shifts just lose their ta_id. Made function to retrieve free shifts for a certain period of time. Moved all the logic into the controller, View only displays information.
Fixed overlapping shifts
Added a bunch of stuff to shifts, Able to drop, bid and take shifts
Fixed error with 'take' button
Added error/success display for shifts. Made colour modification to availaiblity success message
Added error/success messages
Added place holder notifying other TAs of available shift
Merge pull request #25 from andreykul/issue-22

Issue 22 - Basic Logic Done