Feature legpts new

Bogaert has recently published a paper with an improved version of his ```legpts()``` algorithm. 
http://epubs.siam.org/doi/abs/10.1137/140954969 

This branch implements it in MATLAB, and achieves around a 10x speed up over what we currently have (i.e., ht eH-T version). See figures for errors and timings (vs V4 implementation) below.

(Note that ```jacpts()``` is still using H-T and ```hermpts()```, ```lagpts()``` are still using G-L-R).