Do FF's first run during docker *build*

This gets around a few problems caused by the fact that Firefox's first
ever run on a new profile is quiet different from a normal startup. Note
that this only effects Browsh in Docker.

Dockerfile

@@ -19,6 +19,15 @@ RUN rm ./setup_firefox.sh && rm .travis.yml
 # Setup Browsh
 ADD ./interfacer/contrib/setup_browsh.sh .
 RUN ./setup_browsh.sh
+# Firefox behaves quite differently to normal on its first run, so by getting
+# that over and done with here when there's no user to be dissapointed means
+# that all future runs will be consistent.
+RUN TERM=xterm script \
+      --return \
+      -c "/home/user/browsh" \
+      /dev/null \
+      >/dev/null & \
+      sleep 10
 RUN rm ./setup_browsh.sh && rm manifest.json
 
 CMD ["/home/user/browsh"]

interfacer/main.go

@@ -22,7 +22,6 @@ import (
 
 	"github.com/gorilla/websocket"
 	"github.com/shibukawa/configdir"
-
 )
 
 var (
@@ -42,8 +41,8 @@ var (
 	marionette     net.Conn
 	ffCommandCount = 0
 	defaultFFPrefs = map[string]string{
-		"browser.startup.homepage":                "'about:blank'",
-		"startup.homepage_welcome_url":            "'about:blank'",
+		"browser.startup.homepage":                "'https://www.google.com'",
+		"startup.homepage_welcome_url":            "'https://www.google.com'",
 		"startup.homepage_welcome_url.additional": "''",
 		"devtools.errorconsole.enabled":           "true",
 		"devtools.chrome.enabled":                 "true",
@@ -287,7 +286,6 @@ func getConfigFolder() string {
 }
 
 func startHeadlessFirefox() {
-	println("Starting...")
 	log("Starting Firefox in headless mode")
 	args := []string{"--marionette"}
 	if !*isFFGui {