Merge pull request #2 from yulijia/gh-pages

a new post and some update
use the default fig.height=7 to make the plot square (7in x 7in) so that the arrows are perpendicular to the contour lines
this function is complicated, so make the plots larger (8x8)
tags use the "Foo bar" style
CompStat in the old wiki stands for Computational Statistics
change the title of the grad.desc() article
add 'the'
it is 2y^2, not y^2
further tweaks to the article
rebuild the website; a new article, yeah!
a new article 'Make Visual Illusions Graphs in R'