Bumps

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* --parallel defaults to using one process per CPU.
* --pop=-k sets population size to k rather than k times num parameters
* --resume=- resumes from --store=/path/to/store
* use expanded canvas for parameter histograms to make plots more readable
* use regular spaced tics for parameter histograms rather than 1- and 2-sigma
* improve consistency between values of cov, stderr and chisq
* fix handling of degenerate ranges on parameter output
* add entropy calculator using gaussian mixture models (default is still Kramer)
* vfs module allows loading of model and data from zip file (not yet enabled)
* warn when model has no fitted parameters
* update mpfit to support python 3
* support various versions of scipy and numpy

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* add support for parameter serialization

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* restructure parameter table in gui

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* full support for python 3 in wx GUI
* allow added or missing parameters in reloaded .par file
* add dream state to return from fit() call

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* fix source distribution (bin directory was missing)

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* merge in amdahl branch for improved performance
* update plot so that the displayed "chisq" is consistent with nllf
* slight modification to the DREAM DE crossover ratio so that no crossover
weight ever goes to zero.
* par.dev(std) now uses the initial value of the parameter as the center of the
distribution for a gaussian prior on par, as stated in the documentation. In
older releases it was incorrectly defaulting to mean=0 if the mean was
not specified.
* save parameters and uncertainties as JSON as well as text
* convert discrete variables to integer prior to computing DREAM statistics
* allow relative imports from model files
* support latest numpy/matplotlib stack
* initial support for wxPhoenix/python 4 GUI (fit ranges can't yet be set)