Update for latest state of latexml and Travis-CI

[dginev]

A lot of dust has gathered in the Travis devops for the repo. This PR clears up the first layers:

• update to the latest Travis build convenience syntax
• require on latexml 0.8.3
• update to the new locator API @tkw1536 wrote this summer (continuing the first stabs in #121 by @dominique-unruh )
• update the LaTeXML::Common::Config construction in the tests to a more explicit (and reliable) set of initial parameters

Even with this, I focused on test 07 and saw it fail consistently. That specific set of examples tests inlinedef and reveals an interesting live bug in the stex bindings, where the for attribute of an inline definition's <text> element wrongly accumulates out-of-scope symbols. I added a small patch on the way to diagnosing that, but I'd rather file a focused devops PR here, and continue debugging with the next one.

[dginev]

The travis build "fails for the right reasons" here, so merging, and will try to revive at least one of the tests in the suite next.