Set colormap after plotting in 'sifting.py'. Newer versions of matplotlib complain.
Fix bugs in 'sifting.py'.

Objects were renamed, but not all code was updated.
Fix bug where cand was being double-popped when marking duplicate if 'trackdupes' was set to True in 'sifting.py'.
Pass along 'track' to 'candlist_from_candfile' argument in 'read_candfiles' in 'sifting.py'.

Had to modify 'candlist_from_candfile' to accept new parameters.
Merge pull request #34 from plazar/master

Sift-fixes:  Thanks Paul and Patrick!