DOC: update test command in README.md
Changed an `exp` to `np.exp` 

Not a problem with the import pylab, but discovered it when copying/pasting to another script.  Consistent with use of np elsewhere in notebook.
Merge pull request #41 from schodge/patch-1

Changed an `exp` to `np.exp`
BUGFIX: evalF1: sanitize inputs, power
TEST: add test for evalF1, thanks to Shayne Hodge.
TEST: remove exec bit from test_evalF1
TEST: remove exec bit
DOC: run the ipython notebooks with the latest python-deltasigma