Bump version to 0.7.4.1 and add changelog.
|Changed in version 0.7.4.1:|
|* Bump upper bound on base to support ghc-8.4|
|* Use `TChan` from `stm` rather than `Chan`|
|* Update the homepage since trac.haskell.org has shut down|
|Changed in version 0.7.4.0:|
|* Properly process Unicode key events on Windows.|
|* Add an instance MonadExcept IdentityT.|