README edits

[jeremymanning]

• Instructions for installing and running PsychoPy (e.g. PsychoPy download link, link to documentation/instructions) along with version info-- e.g. list whatever the PsychPy version number is that you're using
• Need more documentation about what subject codes and run numbers are. E.g. are subject codes arbitrary unique identifiers for each subject? What do the "run numbers" mean and how do they impact what happens in the experiment?
• Need a more in-depth description of the task, ideally with a figure (or several)
• Add something about this being an EPSCoR Attention Consortium project with a link to the EPSCoR website

[jeremymanning]

Also add a description of how the repo is organized-- e.g. folder structure, what's in each folder, etc.

[KirstensGitHub]

readme has been updated :)