Clarify available themes (#168)
Clarify available themes (#168)

* Clarify available themes

* Make supported theme list explicit

EricFromCanada/sphinx-bootstrap-theme,wildintellect/sphinx-bootstrap-theme,EricFromCanada/sphinx-bootstrap-theme,wildintellect/sphinx-bootstrap-theme,ryan-roemer/sphinx-bootstrap-theme,ryan-roemer/sphinx-bootstrap-theme,EricFromCanada/sphinx-bootstrap-theme,ryan-roemer/sphinx-bootstrap-theme,wildintellect/sphinx-bootstrap-theme