Fix broken/outdated "Read the Docs" pages for ETS projects

[rahulporuri]

The following documentation builds on "Read the Docs" are broken -

• TraitsUI
• Envisage
• AppTools
• Chaco
• SciMath
• MayaVi
• Traits Futures

Note that Traits docs build is working as expected.
Note also that PyFace and Enable don't exist on RtD.

See enthought/traits#1478 to understand how to fix the broken builds.

[rahulporuri]

I'm going to remove MayaVi from the list and close this issue. We're not actively working on MayaVi at the moment so we'll address this issue when we get around to cleaning up MayaVI.