Remove outdated js file
Add TodoApp component and list of constants; fix bugs in stores

Now that there is a skeleton version of the whole front-end "stack"
(dispatcher, stores, and views), we can compile this JS with webpack,
which will start to surface any errors.

Most bugs are a result of my using a different file naming convention
from the tutorial, and then mistakenly copying their 'require'
statements or file naming. There are some such bugs remaining in the
dispatcher that will be corrected next.