Homework 6 (fix)

There was a random crash (kernel restart) happening with f2py code in the previous submission as briefly mentioned in the [notebook](http://nbviewer.ipython.org/github/tomyun/2014_Astr599_HW/blob/3080bce87487f12d73b88e228f0d79f216d565b3/tomyun/HW6.ipynb). I thought that's due to low performance of IPython kernel on my old laptop, but it's found out to be a coding mistake on array indexing. I'd mostly forgotten about 1-based indexing of Fortran and got to notice it while reviewing other student's work.

A weird workaround of drawing in-between small plot is no longer necessary and it seems to work fine with no restart. As the previous pull request (#103) was already merged, I'm opening a new one. Thanks!