add in starage class
Added in basic logic class. not done yet
Added in cases for all the command types available
Merge branch 'master' of https://github.com/cs2103aug2014-w13-4j/main into chuyu-storage
add in throw exceptions
add in two storagess in storage file
add in interfaces for two sub storages
add in basic add, update and delete function, add in some of the basic filter functions
modification of the CRUD functions
add in tasktostring method
add in constants
add in string to task method
add in tag storage
Add and delete method for logic
Merge branch 'master' of github.com:cs2103aug2014-w13-4j/main into pn-logic-crud
Added in update method
Added in select method
remove select method
remove redundant variable declarations
added isCompleted field for task class