Housekeeping and bug fixes

This is the first release for this project in almost two years, so it includes a bunch of fixes. More content should follow.

Starting from 0.3.1, we won't include "-alpha" or "-beta" in the naming scheme, as it is considered irrelevant.

Added

• requirements-dev.txt that contain dev requirements. It makes contribution easier.
• PyCharm configuration files.

Changed

• Animations are now all stored in local variables, and no longer in an "ani" global list of animations.

Fixed

• The main example file strider.py was launching animations for each subprocess.
  This file is now considered an executable.
• evolutionary_optimization_builtin was during the last evaluation of linkages.
• data_descriptors were not save for the first line of data only in geneticoptimizer.
• Multiple grammar corrections.
• The video function of physicsengine.py now effectively launches the video (no call to plt.show required).
• The video function of physicsengine.py using debug=True was crashing.