Color assignment and dates

[vsoch]

We want to minimize changes to the interface, so we should:

• 1. derive the date from the repo instead of when the post was generated
• 2. have pre-assigned colors so the files aren't updated with new color generation

[vsoch]

This is fixed - the dates are from the API and represent when the taxonomy items were last updated. The colors are now pre-assigned and this should lead to many fewer files changed when an interface is updated.