warns users on signup if their chosen username already exists (fixes #273)
Merge pull request #275 from npm/user-already-exists-warning

warns users on signup if their chosen username already exists (fixes #273)
add a `superfluous` css class to unwanted README elements instead of removing them from the DOM
hit *** to toggle display of superfluous readme elements
update readme presenter tests
moar badge domains
fix star alignment
shrink readme font size and set sizes for h345. Fixes #284 and fixes #285
fixes npm-before-time-existed bug + template change