BUG: stats.entropy broken (issue #3030)

stats.entropy will fail when calculate relative entropy of arrays have
ndim > 1. (issue #3030)
assign -inf to vec after call to xlogy
pep8 fix
set the term to be 0 when p[k]=q[k]=0
Merge pull request #3041 from richardtsai/fix_relative_entropy_ndim

BUG: stats.entropy broken (issue #3030)