Suggest using url.$URL.insteadOf to speed up "go get"

By setting the url. option to
git://, when "go get" tries to first download
buildglue from git://, git will
automatically rewrite the URL to use https:// and avoid the
significant delay.

The url.$URL.insteadOf option is documented in the git-fetch manual.

Change-Id: I50ab5b669d5026f011c35c1a19ec0c6dc1b37762
diff --git a/README b/README
index ec421b7..67f41be 100644
--- a/README
+++ b/README
@@ -8,6 +8,10 @@
 Buildglue follows normal Go project conventions, so it can be
 downloaded and installed in just a few steps:
+  # Configure Git to use https:// instead of git://
+  # (Optional, but makes "go get" below much faster.)
+  git config --global url. git://
   # Create a Go workspace (if you don't have one already)
   mkdir buildglue
   export GOPATH=$PWD/buildglue
@@ -18,7 +22,3 @@
 The $GOPATH/src/ directory will now
 contain a clone of the buildglue Git repo, and the $GOPATH/bin
 directory will contain the compiled commands.
-(Caveat: Because currently silently ignores TCP
-connections to port 9418 instead of rejecting them, the "go get"
-command takes longer than necessary to download initially.)