Adding `.dev1` suffix for `api-core` and `spanner` after release. (#4750)

diff --git a/setup.py b/setup.py
index 469ed47..1d2d6db 100644
--- a/setup.py
+++ b/setup.py
@@ -68,7 +68,7 @@
 
 setup(
     name='google-api-core',
-    version='0.1.4',
+    version='0.1.5.dev1',
     description='Core Google API Client Library',
     long_description=README,
     namespace_packages=['google'],