Have Spellcheck in CI

[narendasan]

Might make it easier when doing edits if you had Travis or something spellcheck for you. TIL uses a system that works alright, though we end up having a pretty extensive dictionary to accommodate a lot of weird names and stuff.

• TIL: http://til.acm.illinois.edu/
• Rakefile: https://github.com/acm-uiuc/til/blob/master/Rakefile
• Spec Task: https://github.com/acm-uiuc/til/blob/master/spec/spelling_spec.rb
• Travis Config: https://github.com/acm-uiuc/til/blob/master/.travis.yml
• Dictionary: https://github.com/acm-uiuc/til/blob/master/dictionary.yml

(also btw would be good to use tags to designate different classes of issues)