Add assets/config module, SASS files, templates.

Add:
	bitshift/assets.py
		-add module that contains functions to be called from inside the
		templates/ Jinja HTML files -- currently contains tag(), which generates
		an HTML asset tag based on a filename.

	bitshift/config.py
		-add Flask configuration module.

	static/(sass/main.sass, css/main.css)
		-create isolated directory for SASS files; compiled CSS files will be
		stored in static/css.

	static/css/_mixins.sass
		-add SASS partial to contain mixins (globally relevant to the project's
		styling).

	templates/layout.html
		-add various metadata.