Try using --pvp-bounds both

Try using --pvp-bounds both

Squash of `bounds` branch:

- https://github.com/wincent/docvim/tree/bounds
  (commit 22e92335248334b33d791c179b25fc53a16aafb2)

Based on discussion here:

  http://stackoverflow.com/a/37876041/2103996

Trying this:

- (Almost) no constraints in docvim.cabal file.
- Upload using --pvp-bounds, which produces a docvim.cabal file something like
  this: https://gist.github.com/wincent/145d35bbc75cff2a491fd33fe81d39b0

This effectively means we'll upload something more constrained than what we
tested in Travis, and that is probably OK.

Note that I had to add base upper bounds as noted here:

  https://travis-ci.org/wincent/docvim/jobs/138374403

> ++cabal check
> The following errors will cause portability problems on other environments: *
> The dependency 'build-depends: base' does not specify an upper bound on the
> version number. Each major release of the 'base' package changes the API in
> various ways and most packages will need some changes to compile with it. The
> recommended practise is to specify an upper bound on the version of the 'base'
> package. This ensures your package will continue to build when a new major
> version of the 'base' package is released. If you are not sure what upper
> bound to use then use the next major version. For example if you have tested
> your package with 'base' version 2 and 3 then use 'build-depends: base
> >= 2 && < 4'.
>
> Hackage would reject this package.

See also:

  https://github.com/commercialhaskell/stack/issues/2262