modules: Update github.com/golang/protobuf to v1.2.0 (#160)

diff --git a/go.mod b/go.mod
index 92b8a6d..f449359 100644
--- a/go.mod
+++ b/go.mod
@@ -1,7 +1,7 @@
 module google.golang.org/appengine
 
 require (
-	github.com/golang/protobuf v1.0.0
+	github.com/golang/protobuf v1.2.0
 	golang.org/x/net v0.0.0-20180724234803-3673e40ba225
 	golang.org/x/text v0.3.0
 )
diff --git a/go.sum b/go.sum
index 033d8d7..5e644c2 100644
--- a/go.sum
+++ b/go.sum
@@ -1,8 +1,3 @@
-github.com/golang/protobuf v1.0.0 h1:lsek0oXi8iFE9L+EXARyHIjU5rlWIhhTkjDz3vHhWWQ=
-github.com/golang/protobuf v1.0.0/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
-github.com/golang/protobuf v1.1.0 h1:0iH4Ffd/meGoXqF2lSAhZHt8X+cPgkfn/cb6Cce5Vpc=
-github.com/golang/protobuf v1.1.0/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
-golang.org/x/net v0.0.0-20180724234803-3673e40ba225 h1:kNX+jCowfMYzvlSvJu5pQWEmyWFrBXJ3PBy10xKMXK8=
+github.com/golang/protobuf v1.2.0/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
 golang.org/x/net v0.0.0-20180724234803-3673e40ba225/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
-golang.org/x/text v0.3.0 h1:g61tztE5qeGQ89tm6NTjjM9VPIm088od1l6aSorWRWg=
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=