display for free slot
refactor
improving code quality
support use of TAB to switch between tabs
get rid of magic strings
fix a minor bug in view
add some logging in TickerUI
Merge branch 'UI'
Merge pull request #114 from cs2103aug2014-w15-3J/Logic

Merge Master with Logic
Merge pull request #115 from cs2103aug2014-w15-3J/master

Merge Logic with Master