Add a styleguide stylesheet and setup SASS

[mngyuan]

this PR adds a couple quick new techs to our repo which will likely replace when we package them in with mern, and creates some TODOs for everyone:

• convert your stylesheets to SASS (probably just change the extension)
• add @import 'common'; to the top
• update your html to look for ../css/compiled/filename.css instead of ../css/filename.css

(or i could just do that in this PR if y'all want)

also we should talk about default fonts because the styleguide uses Lato and Montserrat

gulp

The no-longer latest and greatest JS task runner, where you write your build tasks as javascript functions instead of configs. We only have 2 build tasks: compile our Sass, and serve the files on localhost. For now, all this means is you run gulp while developing instead of python -m SimpleHTTPServer or whatever you've been doing.

SASS

A CSS preprocessor with support for variables, nested styles, etc. The docs are really good: http://sass-lang.com/guide
Some notes:

• _filename.scss files are partials, which can't be used as standalone stylesheets but can be used with @import 'filename'; statements. _common.scss and _styleguide.scss are example usages
• you can multiply units (and you should! try 2 * $base-unit)

[mngyuan]

also i went and deleted all the trailing whitespaces in the html because my editor is set up to do that

[ajaska]

Oh, looks like you committed the node_modules directory. I wouldn't recommend that ... instead make a package.json and add dependencies

[mngyuan]

oh, didn't know node updated their recommendation on committing node_modules. i've removed it :)

[ajaska]

Might conflict with #11 and #12 but yolo, looks good to me