Update README.md (#134)

Fix hex docs url

Author: carlosliracl

README.md

@@ -1,7 +1,7 @@
 # An Alternative Elixir Driver for MongoDB
 
 [![Hex.pm](https://img.shields.io/hexpm/v/mongodb_driver.svg)](https://hex.pm/packages/mongodb_driver)
-[![Hex Docs](https://img.shields.io/badge/hex-docs-lightgreen.svg)](https://hexdocs.pm/mongo_driver/)
+[![Hex Docs](https://img.shields.io/badge/hex-docs-lightgreen.svg)](https://hexdocs.pm/mongodb_driver/)
 [![Hex.pm](https://img.shields.io/hexpm/dt/mongodb_driver.svg)](https://hex.pm/packages/mongodb_driver)
 [![Hex.pm](https://img.shields.io/hexpm/dw/mongodb_driver.svg)](https://hex.pm/packages/mongodb_driver)
 [![Hex.pm](https://img.shields.io/hexpm/dd/mongodb_driver.svg)](https://hex.pm/packages/mongodb_driver)