Environment variables minor typo fix (#43)

diff --git a/README.md b/README.md
index a8fc466..80c1dae 100644
--- a/README.md
+++ b/README.md
@@ -75,8 +75,8 @@
 
 Client constructor will read values for the `apihost`, `namespace` and `api_key` options from the environment if the following parameters are set. Explicit parameter values override these values.
 
-- *\_\_OW_API_HOST__*
-- *\_\_OW_NAMESPACE__*
+- *\_\_OW_API_HOST*
+- *\_\_OW_NAMESPACE*
 - *__OW_API_KEY*