add yard to dev deps
add yard tasks to rake
ignore yard_coverage.txt
update README for yard coverage
use yardopts to configure yard, rename task to doc
0.6.1
update readme to endorse tokens
remove photo method in students
add YARDoc comments to clever-ruby
fix documentation errors
Merge pull request #38 from Clever/PROD-365-doc-coverage

PROD-365 - doc coverage
Merge pull request #39 from Clever/PROD-367-yard

PROD-367 - Use YARD for documentation