Machine learning for sequential/streaming data

Example usage:

```
# solve for the "xor" problem using a simple neural net with 1 hidden layer with 2 nodes
inputs = [0 0; 0 1; 1 0; 1 1]
targets = float(sum(inputs,2) .== 1)
# build train/validation/test sets, all with the same data
data = buildSolverData(float(inputs), targets)
datasets = DataSets(data, data, data)
# create the network with one 2-node hidden layer
# the params defines some hyperparameters:
# η := gradient descent speed
# μ := momentum term
# λ := L2-penalty param
# dropoutStrategy
# mloss
hiddenLayerNodes = [2]
net = buildRegressionNet(ncols(inputs),
ncols(targets),
hiddenLayerNodes;
params = NetParams(η=0.3, μ=0.1, λ=1e-5))
# some extra params for the solve iterations
params = SolverParams(maxiter=maxiter, minerror=1e-6)
# fit the net
solve!(net, params, datasets)
# now predict the output
output = predict(net, float(inputs))
# show it
for (o, d) in zip(output, data)
println("Result: input=$(d.input) target=$(d.target) output=$o")
end
```

NNet:

- Basic feedforward network
- Backprop working
- Standard activations/layers (Identity, Sigmoid, Tanh, Softsign)
- Other activations/layers (Softmax, ReLU, LReLU)
- Dropout regularization
- Basic data management (train/validate/test splitting)
- Advanced data cleaning/transformations (handling NaNs, map multinomal classes to dummies, standardizing)
- Basic gradient descent params (early stopping, momentum, L2 penalty)
- Easy network building methods (buildClassificationNet, buildRegressionNet)
- Advanced network building methods (ReLU + dropout, multinomal classification)
- Generalized penalty functions
- Online algo: handle sequential data properly (unbiased validation/test data)
- Cross-validation framework
- Visualization tools (network design, connection weights, fit plots)
- Ensembles

Experimental:

- Spiking neuron model (Leaky Integrate and Fire Neuron based on Spike Response Model)
- Gaussian receptive field for input spike train generation
- Liquid State Machine (LSM) framework
- LSM visualizations
- LSTM layer
- Grid-search for hyperparameters/net design
- GA for hyperparameters/net design
- Readout model tuning

Other:

- Naive Bayes

- Neural net framework with plug and play components
- Simple network building. Give type of problem, desired input/output, and let it figure out a good network design
- Focus on time series and sequential models.
- Recurrent networks, time delay networks, LSTM.
- Mini-batch and single update solvers
- Spiking neural models
- Echo state networks / Liquid state machines