Create README.md

I've tested this python version of fmincg.py with the course material from Coursera/Machine Learning fall 2013 held by Andrew Ng. So far it seems to work well, that is, it gives the same answers than its Octave/MatLab counterpart fmincg.py. So far I've tested it with exercise 3,4 and 5. Otherwise it works fine, but in exercise 4 it doesn't give same predictions than its counterpart.