Grammar, sentence structure, and stylistic changes

I edited the section on *Development Process* to try to make it clearer and tighter, and to clarify some ambiguities in the text.
Verb form agreement in list + missing preposition

Edits to the *Product Owner* section for verb form agreement of items in a list and to add a missing word
Merge pull request #30 from acusti/patch-1

Grammar, sentence structure, and stylistic changes