add JUnit test

-add JUnit test
-add test for splitting user input
add class CommandKey

-add CommandKey for parser to check the command
-add initial code for interpreting command
modify CommandType and CommandKey

-modify CommandType and CommandKey to be used by parser
implement command switches

-implement command switches to allow correct execution of methods for
different command keys
Merge pull request #46 from cs2103aug2014-t16-1j/parser

Parser (Skeleton completed)
-Complete the main skeleton of parser, especially in support of "add"
-The actual implementation is still not completed
-The general idea of what will be return to the UI is implemented