update documentation and make BaseMiner and BaseMinerAPI unable to be instantiated directly. Add more unittests for miners.

docs/miners/base_miner.md

@@ -0,0 +1,10 @@
+# pyasic
+## Base Miner
+[`BaseMiner`][pyasic.miners.BaseMiner] is the basis for all miner classes, they all subclass (usually indirectly) from this class.
+
+You may not instantiate this class on its own, only subclass from it.  Trying to instantiate an instance of this class will raise `TypeError`.
+
+::: pyasic.miners.BaseMiner
+    handler: python
+    options:
+        heading_level: 4