Cache external api results for a set time period

[ericstewart]

Fetched results from the external weather API should be cached for a period of time (initially 30 minutes). This will help with both speed and unnecessary triggering of API rate limiting, when data is not expected to change significantly within a short period of time.

Tasks

• Users should see a visual indication when cached results are displayed
• Ideally cache rendered page fragments for better performance