create prioritzeTask function
create postponeTask function
create massDelete function
create recurringTask function
create addingTags function
Merge branch 'master' into lareina-storage

Conflicts:
	.idea/misc.xml
	.idea/workspace.xml
	cs2103aug2014-W09-3j.iml
	src/tareas/common/Tasks.java
	src/tareas/storage/StorageWriter.java
	src/tareas/storage/TareasIO.java
update changes
remove bugs in massDelete and postponeTask
testing insertTask
added multiple input case in testEditTask