Square system for polynomial case

Found a stream function that gives a square system for the case where N=5.
Check the script polyBasis.m for more information. If N=5 and we are using
a 9 points stecil we should get 18x18 matrix with full rank.
(Lebesgue constant) VS (number of points) plot

Add the script lebesgueConstant.m to generate this plot. It works fine,
however it get slow for N > 11, depending how big is the system and how
condition is the interpolation matrix.
Kosloff & Tal-Ezer mapping added to poly case

Now we can test the different node distributions for the polynomial
interpolant as well. I did the necessary modifications on the related
functions to be able to use fminbnd in the script lebesgueConstant.m.