added termshark and switched to ubuntu base

Dockerfile

@@ -1,5 +1,15 @@
-FROM alpine:edge
-MAINTAINER Daniel Guerra
-RUN apk --update --no-cache add tshark
+FROM golang AS build
+ENV GOPATH=/go
+RUN go get -u github.com/gcla/termshark/cmd/termshark
+
+FROM ubuntu
+
+RUN set -ex; \
+    apt-get update; \
+    apt-get install -y --no-install-recommends \
+    tshark; \
+    apt-get autoremove; apt-get clean; \
+    rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*
+
+COPY --from=build /go/bin/termshark /usr/local/bin/termshark
 COPY bin /bin
-CMD ["sh"]