Update task-execution-over-the-space.markdown

Got through 1/2 of it...

Removing passive verb tense, where possible (it's more wordy and harder for most imperative programmers to understand).
Using class names in place of concepts, where appropriate.
Correcting 4 -> 18 as result of reduce calculation.
Minor structure changes.
Merge pull request #149 from jasonnerothin/patch-3

Update task-execution-over-the-space.markdown