Chore/clean dependencies (#30)

* Disables retry by default

* Update README

* Make tenacity as an optional dependency

* Bump the version to 0.5.0

Author: passren

pymongosql/__init__.py

@@ -6,7 +6,7 @@
 if TYPE_CHECKING:
     from .connection import Connection
 
-__version__: str = "0.4.8"
+__version__: str = "0.5.0"
 
 # Globals https://www.python.org/dev/peps/pep-0249/#globals
 apilevel: str = "2.0"