write to file

[spall]

It seems too complicated right now to address, in fsatrace, the issue where 'out-file' is registered as a read if Rattle is run as follows:

haskell-program-that-runs-rattle &> out-file

So, I just added an option to write Rattle output to a file; which from my testing seems to avoid the problem for whatever reason. I wasn't sure how to meld writing to a file with the RattleUI so I ignored that for now, but will do something with that after I hear your opinion.

[spall]

I wanted to write stdout/stderr and the output of rattle to the same file; to emulate someone doing '&> file'. But I'm not sure how/if the output from the 'rattleUI' should be written to a file, thoughts?