Travis CI setup for integration testing (fixes #530).

Candidate issues to be addressed:

- race condition: start.sh might fail to start Boulder WFE before
  ./tests/boulder-integration.sh is run (unlikely, but possible,
  leading to flaky tests)

- intertwined build logs (./start.sh boostraps in the background,
  integration test debug logs on server and client side)

tests/boulder-integration.sh

@@ -1,8 +1,10 @@
-#!/bin/sh
-# Simple integration test, run as "./boulder-integration.sh auth" or
-# adjust parameters: "./boulder-integration.sh --domain bang auth".
+#!/bin/sh -xe
+# Simple integration test, make sure to activate virtualenv beforehand
+# (source venv/bin/activate) and that you are running Boulder test
+# instance (see ./boulder-start.sh).
 
 root="$(mktemp -d)"
+echo "\nRoot integration tests directory: $root"
 
 # first three flags required, rest is handy defaults
 letsencrypt \
@@ -17,7 +19,4 @@ letsencrypt \
   --domains le.wtf \
   --authenticator standalone \
   -vvvvvvv \
-  "$@"
-
-# print at the end, so it's more visible
-echo "\nRoot integration tests directory: $root"
+  auth

tests/boulder-start.sh

@@ -0,0 +1,15 @@
+#!/bin/sh -xe
+# Download and run Boulder instance for integration testing
+
+export GOPATH="${GOPATH:-/tmp/go}"
+
+# $ go get github.com/letsencrypt/boulder
+# package github.com/letsencrypt/boulder
+#         imports github.com/letsencrypt/boulder
+#         imports github.com/letsencrypt/boulder: no buildable Go source files in /tmp/go/src/github.com/letsencrypt/boulder
+
+go get -d github.com/letsencrypt/boulder/cmd/boulder
+cd $GOPATH/src/github.com/letsencrypt/boulder
+make -j4  # Travis has 2 cores per build instance.
+./start.sh &
+# Hopefully start.sh bootstraps before integration test is started...