Use `mapM_` instead of `() <$ mapM` in one place.
Clean up `mediaTypeOf` a bit.
Use `stripPrefix` where appropriate.
Remove dangling `where` from one function.
Remove redundant isHexDigit function.
Add PatternGuards pragmas.
Slightly fix readability of main program file.
Merge pull request #1486 from Aelve/minor

Very minor cleanup and readability changes