ENH: annotate features in multiple colors

Conflicts:
	trackpy/plots.py

removed white spaces

Conflicts:
	trackpy/plots.py

finished implementing the ability to section particles into different colors in annotate plot

cleanups
Merge pull request #104 from RebeccaWPerry/master

annotate with two different colors based on threshold
CLN: Remove stray debugging print statement.
Merge pull request #119 from danielballan/remove-stray-print

CLN: Remove stray debugging print statement.
FIX/ENH: Allow locate to invert float images by assuming normalization=1.
Merge pull request #118 from danielballan/allow-invert-float-images

FIX/ENH: Allow locate to invert float images (assume normalization)