Added test for the truncnorm.ppf and truncnorm.isf
Fix for ticket #1131: ppf and isf for Lognormal fails on array-like 'loc' or 'scale'
Clarified the meaning of self.a*scale + loc and self.b*scale + loc
Merge branch 'pull-463-ppf-isf' into master.

Reviewed at https://github.com/scipy/scipy/pull/463
MAINT: some cleanups in stats.distribution tests.