Sockrates 0.2.1 — settings focus fix

Fixed

• Could not type in the settings fields on some Linux window managers. A click did not hand
  keyboard focus to the input, so the fields looked dead. Any click on a field now claims focus,
  and the window claims keyboard focus on launch.
• The numeric settings (workers, timeout, latency, refresh interval) now reject non-numeric
  input instead of silently accepting text that would break the next run.