Add error checking during new step generation.
Add ios formatting when writing chunks to streams.
Add ability to output results to HDF5 format.

* affineChainSet::writeToHDF5 outputs the chains and likelihoods
* affineEnsemble::writeToHDF5 adds a bunch of attributes detailing
  the fit parameters, then calls affineChainSet::writeToHDF5 to
  write the chains/likelihoods.
* Add support to example programs.