ENH: use optimize.basinhopping in scipy intro tutorial.

Before anneal() and brute() were used in the text.  They have much worse
performance than basinhopping(), which was introduced in scipy 0.12.0
MAINT: add versionadded for optimize.basinhopping
Merge pull request #122 from rgommers/scipy-tut

ENH: use optimize.basinhopping in scipy intro tutorial.