change to matlab-version libsvm

You may follow the steps to install and use libSVM for Matlab from:
http://wangchihwei.blogspot.tw/2011/05/libsvm-for-matlab.html

You can also download the pre-built .mexw64 files here:
https://www.dropbox.com/sh/cxap6xed7gpey7j/AADNPtMLm9rO3-k4MRuDC0Ofa?dl=0

After installing, please click "Set Path" in Matlab and add the path to
svm tools(libsvm-ver/matlab/), in order to use the commands.

We don't store libsvm data in files now. Instead, we store and pass them
in "label"/"inst" (matlab vector and matrix).
The performance doens't change a lot.