moved elm and random_hidden_layer to neural_networks;
adjusted __init__.py files to match;
changed user_func to xfer_func and made it a string or callable;
adjusted examples and benchmark to compensate for changes;
added 'tanh','sine','hardlim','sigmoid','tribas' transfer funcs to SimpleRHL;
added 'gaussian','poly_spline','multiquadric' transfer funcs to RBFRHL;
change multiquadric to lambda;
moved internal functions out of if/else block into dictionary;
refactored _compute_hidden_activations into BaseRHL;
smoothed the docstrings