Allow use of select PDF path-painting operators

getStyle() now allows direct use of select PDF path-painting operators
rect() now allows postponed style setting
bug fix for lines()'s postponed style check 

A style should be output unless style is explicitly set to null (i.e. a style should be output if style is undefined).
ellipse() now allows postponed style setting
Updating in-code docs re posponed style setting
Merge pull request #209 from bgribaudo/patch-3

Allow style setting postponement for all drawing methods + direct use of select path-painting operators