Review and optimize CSS used across Infusion

We should take the opportunity before the Infusion 2.0 release to review and optimize the CSS used throughout infusion. Here are some examples for things to look at / improve:

• unused styles
• excessive specificity
• use of !important
• unnecessary overrides ( simplify overall styling rules )
• make use of stylus
• concatenate and minify css ( use source maps )
• css linting

see CSS Purge and CSS Stats for inspiration.