completed the sparse coding part

1. deleted the normalize part in the sampleIMAGES.m
2. modified you equations in *Cost.m
3. added DEBUGMODE in sparseCodingExercise.m, so if you wanna check the
*Cost.m, set it to 1, else set it to others except 1
4. use cg instead of lbfs in gradient decent
Merge pull request #2 from TJUmedialab/master

completed the sparse coding part