Community Guidelines - fixes https://github.com/HabitRPG/habitrpg/issues/3801

Do not merge yet! Check with @lemoness first. Also, Alys is still fixing conflicts in the habitrpg-shared PR.

Must be merged at the same time as https://github.com/HabitRPG/habitrpg-shared/pull/311

- Adds Community Guidelines document as described in https://github.com/HabitRPG/habitrpg/issues/3801
- Contains code related to changing staff to be Tier 9 and moderators Tier 8
- Has commented-out code for preventing people from chatting until they have accepted the Guidelines -- to enable that code, edit [views/options/social/chat-box.jade](https://github.com/Alys/habitrpg/blob/communityGuidelines/views/options/social/chat-box.jade#L14) (see comments in that file)

@lefnire:
- I've added some [fontello](http://fontello.com) icons so that we can use a crown to indicate staff members. I put the fontello code at [public/fontello](https://github.com/Alys/habitrpg/tree/communityGuidelines/public/fontello).  Should I move it elsewhere?
- [views/static/community-guidelines.jade](https://github.com/Alys/habitrpg/blob/communityGuidelines/views/static/community-guidelines.jade#L3) contains a short style section at the top for style changes that are needed for just that page. Would you prefer me to move those styles to [public/css/static.styl](https://github.com/Alys/habitrpg/blob/communityGuidelines/public/css/static.styl)?
- [migrations/20140914_upgrade_admin_contrib_tiers.js](https://github.com/Alys/habitrpg/blob/communityGuidelines/migrations/20140914_upgrade_admin_contrib_tiers.js) needs to be run to change staff and mod contrib tiers when this goes live. Also, It's Bailey (9da65443-ed43-4c21-804f-d260c1361596) will need to manually be set to tier 8 (moderator) because she doesn't have a tier at the moment and I can't be bothered adding code just for her. :)