Properly handle the race condition

[mpenkov]

Use synchronization primitives instead of sleeping. This eliminates the need for the timeout parameter. The affected class is effectively internal, so this "should" not affect regular users.

Also fixed the tests: they didn't clean up after themselves.

Added benchmarks.

Fixes #152

[piskvorky]

What does the new benchmark say? Did this PR affect performance much?

[mpenkov]

On MacOS, there is a significant difference.

Before (note time is in seconds):

-------------------------------------------- benchmark: 1 tests --------------------------------------------
Name (time in s)        Min      Max     Mean  StdDev   Median     IQR  Outliers     OPS  Rounds  Iterations
------------------------------------------------------------------------------------------------------------
test                 9.8556  11.3276  10.8173  0.5690  10.9809  0.5847       1;0  0.0924       5           1
------------------------------------------------------------------------------------------------------------

After (note time is in ms):

------------------------------------------------ benchmark: 1 tests ------------------------------------------------
Name (time in ms)          Min       Max      Mean   StdDev    Median      IQR  Outliers     OPS  Rounds  Iterations
--------------------------------------------------------------------------------------------------------------------
test                  338.2111  401.0051  355.2427  26.0633  344.9050  23.6982       1;1  2.8150       5           1
--------------------------------------------------------------------------------------------------------------------

On Linux, there is no difference in performance, but I could not reproduce the problem, the benchmark times are about the same (~300ms).

[piskvorky]

Oh wow, 30x slower now? We'll have to look into that, that's too much. I'll try to check too (I have a macbook).

[mpenkov]

No, it's the other way around. Before it was 10s, now it's 338ms (0.338s).

[piskvorky]

Oh yes, I missed the bracket with "note" of course :) Sorry.

Great job!