Teperature only goes up

Created by: cmm

Liquidprompt version: master

Steps to Reproduce

1. Set LP_TEMP_THRESHOLD to something reachable
2. Reach the threshold
3. Observe the red and bold temperature appear in your prompt
4. Let the computer cool down
5. Observe the highest-measured temperature lingering in new prompts of the same shell

Expected Behavior

Temperature should update in every prompt (the sample is taken anyway).