Some new functions

• Allow user to specify num_of_global_fittest, fixes #12 .
• Use error_chain.
• Add output_every, to only output every nth time a new fittest individual is found.
• Add share_every, to only share fittest individual after a number of iterations.

Fixing bugs, some new features

• Write output into a log file instead of using print!().
• Remove new() from trait Individual, provide reset() instead.
• All mutexes removed.
• User must now provide whole population but can now use shared configuration / data instead of using lazy_static.
• Calculate_fitness now needs (&mut self).
• Add option share_fittest to share the fittest individual between all population after each iteration.
• Add ocr2 example.
• Add optional method new_fittest_found() to write out some statistics. Default implementation does nothing.
• Add fitness counter statistic to population.
• Fix bug in parallelization using jobsteal.
• Fix bug in TSP2 example.

Multiple populations

This release contains:

• Code refactoring.
• Better documentation.
• Bug fix in the example.
• Allow user to add multiple populations to a simulation.
• Multi-Threading: Now for each population instead for each individual.

Polish

This fixes typos and clippy warnings. The only new feature: allow user to specify reset limit.