doc(README.md): add verb back

Author: Aaron Schlesinger

README.md

@@ -34,7 +34,7 @@ The Deis project welcomes contributions from all developers. The high level proc
 
 ## Docker Based Development Environment
 
-The preferred environment for development uses [the `go-dev` Docker image](https://github.com/deis/docker-go-dev). The tools described in this section to build, test, package and release each version of Deis.
+The preferred environment for development uses [the `go-dev` Docker image](https://github.com/deis/docker-go-dev). The tools described in this section are used to build, test, package and release each version of Deis.
 
 To use it yourself, you must have [make](https://www.gnu.org/software/make/) installed and Docker installed and running on your local development machine.