Check AsyncioDispatcher loop is running

[AlexanderWells-diamond]

Also added documentation. Also fixed potential permanent block in tests - if the subprocess never creates its Client, the parent process blocks forever on an accept(). This was the case in the asyncio_ioc_override, where initialization was failing due to non-running loop.

Closes #95.

[codecov[bot]]

Codecov Report

Merging #96 (52bebac) into master (e3d5590) will increase coverage by 0.02%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master      #96      +/-   ##
==========================================
+ Coverage   87.60%   87.63%   +0.02%     
==========================================
  Files          13       13              
  Lines         928      930       +2     
==========================================
+ Hits          813      815       +2     
  Misses        115      115              

Impacted Files	Coverage Δ
softioc/asyncio_dispatcher.py	92.85% <100.00%> (+0.54%)	:arrow_up:

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Unit Test Results

     15 files  ±  0       15 suites  ±0   21m 19s :stopwatch: +40s    225 tests +  1     219 :heavy_check_mark: +  1      6 :zzz: ±0  0 :x: ±0  3 375 runs  +15  2 940 :heavy_check_mark: +15  435 :zzz: ±0  0 :x: ±0 

Results for commit 52bebac0. ± Comparison against base commit e3d55902.