Added documentation in API.ipynb for the support of learning rate and regularization parameters in SimpleSGDTrainer and for lookup parameter initialization from an existing array.
Added documentation in API.ipynb for the support of learning rate and
regularization parameters in SimpleSGDTrainer and for lookup parameter
initialization from an existing array.

dhgarrette/cnn,Peilun-Li/dynet,kamigaito/cnn,Abasyoni/dynet,mitchellstern/dynet,dhgarrette/cnn,Abasyoni/dynet,cherryc/dynet,cherryc/dynet,Abasyoni/dynet,Peilun-Li/dynet,Peilun-Li/dynet,kamigaito/cnn,cherryc/dynet,dhgarrette/cnn,mitchellstern/dynet