Tidal listener update and rework

[polymorphicengine]

I finally found the time to rework the tidal-listener with all the things i discovered while developing tidal-gui.

tidal-listener is now capable of interpreting any haskell statement (i.e. expressions of type IO a), in that way it is now very similar to ghci, trying to show the value resulting from the statement if possible.

further, let and bindings of the form x <- statement are also valid statements that will bind variables that are kept in memory by the interpreter

for a full list of commands and commandline arguments see the README

[yaxu]

Oh excellent !