Incursion uses 100% of the CPU core it runs on

[RMTEW FULL NAME]

Yield a little, eh?

[RMTEW FULL NAME]

Main input loop now checks for input around 20 times per second, at most. Reduces CPU usage from a constant 50% while idle waiting for user input, to perhaps 2% (sampled anecdotally and non-scientifically). Closes #43

→ <<cset 233f5c43eb8d>>

[RMTEW FULL NAME]

Issue #55 was marked as a duplicate of this issue.