Use char type for circle_perimeter method for speedup
Use same cython directives for whole source file
Fix PEP8 issues
Merge pull request #412 from ahojnnes/draw-cython-directives

ENH: Some improvements to draw.
Merge branch 'master' of git://github.com/scikit-image/scikit-image

Conflicts:
	skimage/draw/_draw.pyx
Merge branch 'master' of git://github.com/scikit-image/scikit-image
ENH: Adding color deconvolution method to convert to an Haematoxylin-Eosin-DAB colorspace
ENH: Added an Immunohistochemical image example
FIX: the rgb2hed function. Legal issues regarding the ihc image. ENH: added the hed2rgb function.
ENH: Added rgb2hed and hed2rgb to __all__ list
FIX: Simplified deconvolution equations
ENH: Added a short test to validate rgb2hed and hed2rgb conversion
FIX: Removed unused dependency
FIX: Ran autopep8 on colorconv.py FIX: modified color.data.ihc function FIX: smaller ihc.jpg image
FIX: modified color.data.ihc docstring.
FIX: import rgb2hed and hed2rgb in the test_colorconv script.
FIX: Fixed test_hed_rgb_roundtrip.
FIX: Testing for ubyte and float images. Input dtypes are converted beforehand.
FIX: img_as_ubyte function threw ValueError due to floating point errors in hed2rgb function.

Clipping the output of the hed2rgb function between 0 and 1 seems to correct
the bug without affecting the conversion quality.
ENH: Added example to the gallery for ihc staining separation