add andres method for circle_perimeter
fix variable
fix docstring + PEP8
add references
Merge pull request #410 from sciunto/circle

Circle perimeter: add new method: Andres
Fix typo in doc string
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.