Ensure that the input array is contiguous
Ensure that the input array is contiguous

This change was spotted in a commit by Michael Schubert (mschubert)
<mschu.dev@gmail.com> in the danielfrg/tsne fork. That commit is
https://github.com/danielfrg/tsne/commit/22e2115800f3bea63c6e61f7a1aa4346b2950719
and touches a whole lot of stuff that doesn't exist here.

douglasbagnall/py_bh_tsne,douglasbagnall/py_bh_tsne