Add 'testWithApplication'' function

[EduardSergeev]

Add testWithApplication' function:

testWithApplication' :: Application -> (Port -> IO a) -> IO a

same as testWithApplication function

testWithApplication :: IO Application -> (Port -> IO a) -> IO a

but accepts Application as a pure argument
The requirement of testWithApplication to pass Application parameter in wrapped in IO monad seems unnecessary strict:
Apparently the only action testWithApplicationSettings (the underlying implementation) does is to unwrap it with:

testWithApplicationSettings :: Settings -> IO Application -> (Port -> IO a) -> IO a
testWithApplicationSettings settings mkApp action = do
  callingThread <- myThreadId
  app <- mkApp
  let wrappedApp request respond =
        app request respond `catch` \ e -> do
  [truncated]

into app which can be done outside of testWithApplication' with:

testWithApplication :: IO Application -> (Port -> IO a) -> IO a
testWithApplication mkApp action =
  mkApp >>= flip testWithApplication' action

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[snoyberg]

I'm ambivalent about this change overall, since either way it's easy to work around (either monadic bind or an additional pure). I'd ask for a different function name though, since a simple tick at the end doesn't express "pure instead of wrapped in IO" to me.