Fixes #72.

Fixes #87.

Similar to `KillLine`, add two new "keys" `ReverseSearchHistory` and `ForwardSearchHistory` which bind to the incremental history search functionality.

Original patch by @boris-stepanov (#90).

Fixes #3.

Fixes #21, which noted that the `LICENSE` file was inconsistent with
`License: BSD3` in the .cabal` file.

Removes `System.Console.Haskeline.MonadException`; now
we use class constraints from `Control.Monad.Catch`.

- Use Travis's build-in apt support
- Use `language: c` explicitly
- Remove unnecessary `cabal` invocations
- Remove the separate `before_install` step

Also:
- Add CI testing up to ghc-8.6.1
- Don't install explicit Cabal versions, now that we don't have
  a custom Setup script.

Haskeline doesn't have a custom Setup script, so that step isn't
providing any value.

Helps fix `stack upload`.

Bump upper bound on containers

Bump stm upper bound

Bump upper bound on unix to < 2.9

See https://ghc.haskell.org/trac/ghc/ticket/15042.

Bump upper bound on base to < 4.13

See https://ghc.haskell.org/trac/ghc/ticket/15018.

Also bump to 0.7.4.2.

Unfortunately trac.haskell.org doesn't exist anymore.

Import Control.Concurrent.STM in Win32 backend

Move away from Chan to STM

The isEmptyChan broken has been long known to be broken

Make sections Markdown correct in README.md

Change to simple build-type & minor ver increment

A minor version increment is required relative to 0.7.3.1 due to the
recent API addition of the `MonadExcept IdentityT` instance

The logic in Setup.hs doesn't affect the build per-se, but rather
prints out a purely informational warning on non-windows systems
in case `terminfo` is disabled. However, the upcoming Cabal 2.0 API
breaks the Setup.hs script so it's easier to just convert to simple
build-type and avoid the additional complexity and overhead.

Add MonadException IdentityT instance