Performance improvements and bugfixes

Hi Sam :)

I put instructions to install the decide-config binary in the last release, but I'm copying them here (let me know if it doesn't work):

1. Download the binary decide-config file.
2. Make the file executable:

cd /mnt/c/Users/mosel/Downloads/
chmod +x decide-config

3. Move the file into your PATH: sudo mv decide-config /usr/bin
4. Run decide-config --help to see options and verify that it worked.

changelog

• keys (the list of all possible responses) is no longer required in experiment.yml as it is now encoded directly into the program
• segmented files are now generated more efficiently
• correct_choices.yml now tries to evenly divide stimuli into the various correct responses (instead of picking randomly and independently for each stimuli). I know we already had to fix this in the old javascript version, but I temporarily forgot