Added throw exception if modification of data
Implemented search for repeating and search for expired tasks
Merge branch 'Logic' of https://github.com/cs2103aug2014-w15-3J/Ticker.git into Logic
Implemented catch for storage exception and search for expired tasks
Merge pull request #115 from cs2103aug2014-w15-3J/master

Merge Logic with Master
Merge pull request #116 from cs2103aug2014-w15-3J/Logic

Merge Master with Logic