Add geometry.curves module.
Add geometry.curves module.

This module is ported from Glumpy, and contains code to generate
vertices for bezier lines.

RebeccaWPerry/vispy,dchilds7/Deysha-Star-Formation,Eric89GXL/vispy,Eric89GXL/vispy,michaelaye/vispy,inclement/vispy,julienr/vispy,inclement/vispy,RebeccaWPerry/vispy,Eric89GXL/vispy,dchilds7/Deysha-Star-Formation,srinathv/vispy,jdreaver/vispy,sbtlaarzc/vispy,QuLogic/vispy,jdreaver/vispy,sbtlaarzc/vispy,kkuunnddaannkk/vispy,ghisvail/vispy,michaelaye/vispy,ghisvail/vispy,drufat/vispy,inclement/vispy,QuLogic/vispy,julienr/vispy,drufat/vispy,jay3sh/vispy,jay3sh/vispy,julienr/vispy,michaelaye/vispy,bollu/vispy,srinathv/vispy,bollu/vispy,dchilds7/Deysha-Star-Formation,ghisvail/vispy,drufat/vispy,kkuunnddaannkk/vispy,kkuunnddaannkk/vispy,QuLogic/vispy,sbtlaarzc/vispy,RebeccaWPerry/vispy,bollu/vispy,jdreaver/vispy,srinathv/vispy,jay3sh/vispy