Stretch: Memoize/cache some GET calls

[twodarek]

GET calls that could be cached (for even 30 seconds):

• get schedule
• get times
• get rooms

Possible options:

• https://github.com/kofalt/go-memoize
• https://godoc.org/golang.org/x/tools/internal/memoize
• https://github.com/bradfitz/gomemcache