Added two helper functions

find-pulse-{monitor,mic} both try to find the internal audio monitor and
the mic (respectively) so I don't have to hard code them.
Updated quickcast

Now the name of the file to use and the date are two different
bindings. This is the beginnings of recording my mic and video separately.
Changed 'filename' to 'vid-filename'

This is another part of my move towards recording mic and internal audio
separately. I might eventually try to record video and all audio as
individual files.