Added sequential minimum optimization algorithm for SVM (#508)

* Implementation of sequential minimal optimization algorithm

* Update smo.py

* Add demonstration of svm partition boundary

1:Use matplotlib show svm's partition boundary
2:Automatically download test dataset

* Update smo.py

* Update smo.py

* Rename smo.py to sequential_minimum_optimization.py

* Update doc and simplify the code.

Fix filename typo error in doc.
Use ternary conditional operator in predict()

* Update doc.