Revert #12260 "BUG: Make Styler ignore None index names to match to_html..."
Master started failing on https://github.com/pydata/pandas/pull/12260 [travis](https://travis-ci.org/pydata/pandas/builds/113480877). Not entirely sure why yet, but was able to reproduce one of the failures locally, and fix it with the revert.

I'll followup later with the actual changes made in #12260 later.
 The TestYahooOptions is in any case not related, as I get the same error when using pandas 0.16.2. So probably something changed on the Yahoo side.
 And I just got a success and then a failure on master for the Yahoo tests, seems to be intermittent.
 yeh we should just disable some more of these yahoo tests
 Going to close this one then.
