[Fix #149] Do not flush temporary files to disk
Update credits

Thank you, @BinaryKhaos
Merge branch 'BinaryKhaos-performance'

* BinaryKhaos-performance:
  Update credits
  [Fix #149] Do not flush temporary files to disk
Do not throw away previously marked overlays
Never loose process state

Mark current process and marked overlays as permanent local variables,
because we must not loose this information if the major mode is changed.
Otherwise we might leave dead processes or outdated overlays around.
Fix process cleanup

Reset `flycheck-current-process` and the mode line in the right buffer,
and regardless of whether the mode is actually enabled or not.