Fix graph overlaps and some typos.

[dan-pandori]

Add a helper function for plotting to avoid the plots overlapping each other.

• Helper function is just copying the first plotting cell, for most intents and purposes.
• Also fix some typos.

Tested by running all cells in: https://colab.research.google.com/github/dan-pandori/rl-tutorial-jnrr19/blob/typos/3_multiprocessing.ipynb

And confirming that everything runs and the plots don't overlap each other.