fixed loss-of-precision issue in util.write_params
catch ImportError when testing inline in integrate.py

Saw ImportError on a Windows system (not sure what caused it).
added miriam annotation output to sbml export
added copy of earm estimate_lopez_embedded.py as fig6 script
updated fig6 script to produce proper plots
added numpy to doc requirements
calculate bng path on demand instead of module load
added sympy to doc requirements
mocked scipy in sphinx environment for RTD
post-0.1.9 updates to vm and docs
fix for long-line continuations produced by some BNG versions
removed debug print
fixed BNG export of multi-pattern observables
refactored some RuleExpression construction logic
massive documentation improvement to core
improved documentation on annotation
top-level docstring and other doc cleanups in macros
improved documentation on bng module
switch to a hierarchy of macros in kinase cascade example
improve integrator efficiency

eliminate a numpy array allocation inside rhs