Add experimental spline interpolation support

A new parameter named useSplines has been added. It is FALSE by default. This parameter makes use of splines rather than lines to connect the points on parallel axes. Only side-effect I can observe is that X axis is continuous now, which keeps us from seeing variable labels.
version bump... trying at beginning of development this time
removed extra branch from travis
grabs the panel grow and prints it.

needs to work on internal and external.  Kept old plotting methods to
pull from for later.

look at commented examples above function def
move spacing to be an arg
move plot generation to be only done once
remove old commented code
white space and small comments
fixed bottom and left labels. removed small spaces on left and bottom of matrix
added grid.draw to be imported
move comments
fixed layout issue
changing default of ggpairs axisLabels to 'show'
works with internal, none, and show labels
moved old print method to a sep file
better arg matching on axisLabel
updated names and value for pring.ggpairs
updated print.ggpairs example
removed old comments
update to better example using color