Edit README files for clarity

This commit contains several minor edits to the project's README files:

-Main project README has been updated with contribution notes and
 contributors.

-app/store/Readme.md has been edited for word choice. Notices
 regarding the current state of the project have been elevated.

-app/view/Readme.md has been edited for clarity regarding content that
 is referenced between views.
Merge pull request #1 from osu-cass/feat_3780_README_round1_edit

Edits look good.