FIX website: css hickup
Added contributing subsection and fixed link to web doc
SGD and SVC duplicate example sorted
sort out plot_iris vs plot_svm_iris
some cosmetic commits and delete duplicate files
No whitespaces at the end of file
common test for sparsify + fix for SGDRegressor
sparsify test: add multi-class test too
Merge pull request #2571 from edran/readme

Added contributing subsection to README