Shell changes

Shell changes
Ignore commit
Merge branch 'master' of https://github.com/neha01mittal/HRRN

Conflicts:
	src/sg/edu/nus/comp/cs4218/impl/Shell.java
	src/sg/edu/nus/comp/cs4218/impl/extended1/PipingTool.java
	test/sg/edu/nus/comp/cs4218/impl/ShellTest.java