Added a websocket connection listener

[cymp]

No description provided.

[codecov]

Codecov Report

Merging #13 into master will decrease coverage by 0.24%.
The diff coverage is 57.14%.

@@             Coverage Diff              @@
##             master      #13      +/-   ##
============================================
- Coverage      83.4%   83.15%   -0.25%     
- Complexity      245      246       +1     
============================================
  Files            31       31              
  Lines           741      748       +7     
  Branches         28       28              
============================================
+ Hits            618      622       +4     
- Misses          112      115       +3     
  Partials         11       11

Impacted Files	Coverage Δ	Complexity Δ
...ava/com/github/ccob/bittrex4j/BittrexExchange.java	76.61% <57.14%> (-0.51%)	53 <1> (+1)

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[cymp]

I just added a listener, no unit test that needs to be implemented here again.

[CCob]

Great. Thanks for the PR. I released 1.0.5 a few days ago which contained your last PR's. I'll pull this into develop for now.