Improving SVM binary classification model on new dataset
Online learning for SVMs is supported only for certain SVM options (a linear SVM with SGD can easily update for example).  

There are implementations out there to address the issue of online learning for all SVMs.

https://stats.stackexchange.com/questions/26041/can-svm-do-stream-learning-one-example-at-a-time

If your model isn't terribly large it also probably isn't too bad to train a new one on all data periodically.