First draft (untested but feature complete) of the IR tripwire version
of the code.  Removed irrelevant parameters from parameters.py, but not
yet the obsolete detector classes.
Repaired small bug in iron_curtain.py.  The code now works!
Rotated image by 180 degrees and removed three obsolete files.
Updated README.md to reflect introduction of IRon curtain.
Updated documentation of the iron_curtain module.
Added IR sensor pin to parameters, changed default value.
Added parameter controlling the rotation of the photo when it's taken.