Update tools for misspell.

build/Dockerfile

@@ -1,7 +1,7 @@
 FROM golang:1.5.2
 ENV GO15VENDOREXPERIMENT 1
-RUN apt-get update && apt-get install -y libpcap-dev python-requests time
-RUN go get github.com/golang/lint/golint github.com/fzipp/gocyclo
+RUN apt-get update && apt-get install -y libpcap-dev python-requests time file
+RUN go get github.com/golang/lint/golint github.com/fzipp/gocyclo github.com/client9/misspell/cmd/misspell
 RUN go clean -i net && go install -tags netgo std
 RUN go install -race -tags netgo std
 COPY build.sh /