Add `go get` to populate the vendor file (#967)

* Add go get to populate the vendor file

* Use dependency manager in Readme
diff --git a/README.md b/README.md
index 4df08c5..4b2cac5 100644
--- a/README.md
+++ b/README.md
@@ -57,6 +57,7 @@
 ```sh
 $ cd $GOPATH
 $ go get github.com/apache/incubator-openwhisk-wskdeploy  # see known issues below if you get an error
+$ go get github.com/tools/godep # get the dependency manager
 ```
 
 ### Build the binary
@@ -64,6 +65,7 @@
 Use the Go utility to build the ```wskdeploy``` binary as follows:
 ```sh
 $ cd src/github.com/apache/incubator-openwhisk-wskdeploy/
+$ godep restore
 $ go build -o wskdeploy
 ```