v0.1.9

Minor release.

New features

• Added option to limit threads used per process when sampling chain in parallel with max_threads_per_process option to sample_chains* methods if threadpoolctl is installed.

Bug fixes

• Fixing non pass through of call counter on state copy. Bug introduced in fdea526 when switching state._call_counts from dictionary to collections.Counter instance which meant call counter not shared by all copies of state which is intended behaviour to ensure that all calls are recorded.
• Changed to always reinitializing integrator step size at beginning of sampling stages with step size adaptation engaged. Changes from previous behaviour of not reinitializing step size of
  integrator if previously set on beginning of adaptive sampling stage, which occured if for example step size was set manually when constructing integrator or had been set in a previous adaptive
  chain stage. Instead when using step size adaptation the integrator step size is now always reinitialized to a reasonable value when initializing the adapter, which ensures the initial step size is appropriate if e.g. the metric has been changed or a previous chain (when running sequential chains) had adapted to a step size inappropriate for the position in state space of the current chain.
• Adjusted step size initialization logic to be robust to cases where Hamiltonian function may evaluate to NaN at some states
• Fixed bug with exception variable not being initialized in edge case of sample chains call with zero length collection of initial states.
• Removed faulty custom subclass / instance check behaviour for matrix classes.