Hyperlink haddocked a few 'run's in Tutorial
Merge pull request #53 from tonyday567/haddock-style

Hyperlink haddocked a few 'run's in Tutorial
Updated documentation
Added 'toList'
Updated tutorial
Improved tutorial introduction
Changed back code blocks to not use hyperlinks

Tony mentioned that using @-style comments for code samples makes them difficult
to read the raw markup and I also found them a bit visually distracting.
However, I chose to keep the hyperlinks for stand-alone type signatures.
Updated tutorial
Added 'debug' function
Added INLINABLE pragma for 'next'
Changed 'debug' to the more general 'yieldAfter'
Added back `debug` for convenience
Updated documentation of the Pipes module

Tony asked about the meaning behind behind what '>~' and '~>' do, so I changed
the headers for the 'Producer' and 'Consumer' sections to better explain how
the details of how they work rather than use vague words.
Clarified `yieldAfter`

I add the implementation of `debug` to the haddocks to make it obvious how you
would use `yieldAfter` and grouped the two together.
Changed documentation for `yieldIf` to use foreach style
Updated tutorial
Updated tutorial
Updated tutorial
Removed the advice on multiple folds, which will be replaced by composable left
folds later.
Changed haddocks for 'for' and ('~>') to show return values