Implement homepage redesign

To see data on the homepage run the following cron jobs:

`./manage.py cron update_reps_ical`
`./manage.py cron update_openstandard`
`./manage.py cron update_tweets`

This PR needs to merge after the /contribute page, as some links need to be updated to point to pages not yet in master.

I still have some tidying up to do, but this should be close enough for code review to begin.
I tried this, but if we combine them then browsers will trip up on the selectors they don't recognize, so the styles would never be applied :cry: