Support GHC 8.8

[chshersh]

Not much has changed. Probably some CPP around MonadFail will be required.

• https://downloads.haskell.org/~ghc/latest/docs/html/users_guide/8.8.1-notes.html#base-library

But mostly:

• Bump up base version
• Bump up versions of other libraries
• Update Travis, CHANGELOG, etc.