remove the Makefile and the fake Rnw; R 3.0 do not require them any more
make the package depend on R 3.0.0, and specify the vignette builder to be knitr
need to load the corrplot package in the vignette
rename index.Rmd to corrplot-intro.Rmd so that index.html is not overwritten
Merge pull request #2 from yihui/master

buidl R Markdown vignettes under R 3.0.0