Update protocol (#136)

## What is the goal of this PR?

We updated protocol to 2.0.0a3 from the public PyPi repo.

Author: Alex Walker

BUILD

@@ -80,7 +80,7 @@ assemble_pip(
     author_email = "[email protected]",
     license = "Apache-2.0",
     install_requires=[
-        'graknprotocol==0.0.0-6bf8c601ecd57a2869cde56c17eec8784a9a2804',
+        'graknprotocol==2.0.0a3',
         'grpcio==1.33.2',
         'protobuf==3.6.1',
         'six>=1.11.0',

requirements.txt

@@ -17,8 +17,8 @@
 # under the License.
 #
 
---extra-index-url https://repo.grakn.ai/repository/pypi-snapshot/simple
-graknprotocol==0.0.0-6bf8c601ecd57a2869cde56c17eec8784a9a2804
+# --extra-index-url https://repo.grakn.ai/repository/pypi-snapshot/simple
+graknprotocol==2.0.0a3
 grpcio==1.33.2
 protobuf==3.6.1
 six>=1.11.0