Update requirements (#21)

Author: skkumaravel

requirements.txt

@@ -1 +1,2 @@
 grpcio==1.18.0
+protobuf==3.6.0

setup.py

@@ -2,7 +2,7 @@
 
 
 setup(name='iosxr_grpc',
-      version='1.2',
+      version='1.3',
       description='gRPC library for IOS-XR > 6.1.1',
       url='https://github.com/cisco-grpc-connection-libs/ios-xr-grpc-python',
       author='Karthik Kumaravel',
@@ -11,5 +11,6 @@
       packages=['iosxr_grpc'],
       install_requires=[
           'grpcio==1.18.0',
+          'protobuf==3.6.0',
       ],
       zip_safe=False)