We seperate features to members. At the beginning, we both writing parse part, 
One use lex/yacc and one use traditional way. Then traditional way reach the 
goal earlier alone with builtins. 
After this, both two members continue working on traditional parse method based
version. One finished redirections and one finished background, pipe and memory 
releasing. 

The following is the extra testing samples we used:

>>>><<<<<<|||||&&&&&
cd
cd ~
cd ~/final_assignment/sish-mhan-sgao
cd ~donut
cd ~donut/final_assignment/sish-mhan-sgao
cd ~nobody
cd argument1   argument2
exit dkjfowei  df\
ls -al|echo 1111111$$$$$ $$?333$?$?$?$??24543$ $$$
echo $$$$123$$12$$$1234$????$?$$    	$?$$$e
echo "saoeijf osdjf d j     sjdf $?$$??$}?"

|||||
ls|cat|wc -l
ls|
ls|&cat
ls&&&
abcd|efg|
ls|acg
cat|ls
ls -al >>out|cat|wc
pwd>out|cat
abcd|cat
cat|abce
ping google.com|cat
cat|ping google.com

./sish -c ls -al | cat > outcat