Remove Messenger actor and use withContext instead

[twyatt]

Inspired by comment by elizarov (on Jun 15) in Kotlin/kotlinx.coroutines#87:

when you ask an [sic] actor and want a result back the proper design would be to have a suspend fun with a normal (non-deferred) Result. However, please note that this whole ask & wait pattern is an anti-pattern in actor-based systems, since it limits scalability.

Additionally, changing over to using withContext made the library much easier to write tests for.

Took the refactor opportunity to:

• Update the Kotlin Coroutines library and integrate Flow for data streams
• Drop experimental from package name (since we're no longer using experimental Coroutines)
• Update copyright headers
• Write/utilize JUnit test rule that only outputs debug logs on test failure
• Add Kotlinter
• Write lots of unit tests

[codecov]

Codecov Report

Merging #31 into develop will increase coverage by 54.00%.
The diff coverage is 74.48%.

@@              Coverage Diff               @@
##             develop      #31       +/-   ##
==============================================
+ Coverage      20.37%   74.38%   +54.00%     
- Complexity        17       35       +18     
==============================================
  Files             14       14               
  Lines            476      242      -234     
  Branches          42       28       -14     
==============================================
+ Hits              97      180       +83     
+ Misses           368       52      -316     
+ Partials          11       10        -1     

Impacted Files	Coverage Δ	Complexity Δ
core/src/main/java/android/BluetoothDevice.kt	0.00% <0.00%> (ø)	0.00 <0.00> (ø)
core/src/main/java/logger/Logger.kt	0.00% <0.00%> (ø)	0.00 <0.00> (?)
processor/src/main/java/GattProcessor.kt	100.00% <ø> (ø)	4.00 <0.00> (?)
timber-logger/src/main/java/AndroidTagGenerator.kt	71.42% <ø> (ø)	3.00 <0.00> (ø)
timber-logger/src/main/java/TimberLogger.kt	0.00% <ø> (ø)	0.00 <0.00> (ø)
core/src/main/java/logger/AndroidLogger.kt	33.33% <33.33%> (ø)	1.00 <1.00> (?)
core/src/main/java/gatt/CoroutinesGatt.kt	51.42% <51.42%> (ø)	8.00 <8.00> (?)
throw/src/main/java/GattOrThrow.kt	83.33% <71.42%> (ø)	0.00 <0.00> (?)
core/src/main/java/gatt/Events.kt	75.40% <75.40%> (ø)	0.00 <0.00> (?)
core/src/main/java/gatt/GattCallback.kt	83.33% <83.33%> (ø)	16.00 <16.00> (?)
... and 14 more

[Chris-Corea]

Great job, dude. Holy moly.

[davidtaylor-juul]

🚀 and tests 💯