Update README

Author: Jonathon Belotti

README.md

@@ -6,13 +6,23 @@ Contains Bazel rules to fetch and install Python dependencies from a requirement
 
 In `requirements.txt`
 ```
-cryptography[test, docs]
-boto3
+cryptography[test, docs]==2.8
+boto3==1.9.253
 ```
 
 In `WORKSPACE`
 ```
-load("@rules_pip//:defs.bzl", "pip_repository")
+rules_python_external_version = "37dad8910495ad71bae391db7a843a0f7a3ea902"
+
+git_repository(
+    name = "rules_python_external",
+    commit = rules_python_external_version,
+    remote = "[email protected]:dillon-giacoppo/rules_python_external.git",
+    shallow_since = "1572846707 +1100",
+)
+
+
+load("@rules_python_external//:defs.bzl", "pip_repository")
 
 pip_repository(
     name = "py_deps",