Add some TH exports that are helpful.
Restrict Travis to work only with master and release branches.

Fixes #51.
Describe the GHC version situation for promoted Eq instances.

This fixes #52.
Update comment for bindTyVarsClause (#37)
Update to README, fixing #37 as wontfix.

README still needs more updating. This commit just focused on
the list of supported features.
Link to #37 in README for the curious.
Add exporting Symbol to Preludes.
Some preliminary work on #31

Prelude modules are commented out in .cabal file. Defunctionalization
symbols use eta-expanded type and so do the type families. However
clauses are not yet extended with extra parameters as I don't know
what to do when there is no type signature.