For development statically link dcc-rs

This links the python bindings statically to libdeltachat.a if the
DCC_RS_DEV environment variable is set to the project's root.  This is
a little simpler then requiring the manual CFLAGS and LD_LIBRARY_PATH
tweaking.

It also adds a script to easily invoke the integration tests locally
without forgetting steps.

run-integration-tests.sh

@@ -0,0 +1,29 @@
+#!/bin/bash
+
+# Small helper to easily run integration tests locally for development
+# purposes.  Any arguments are passed straight to tox.  E.g. to run
+# only one environment run with:
+#
+#   ./run-integration-tests.sh -e py35
+#
+# To also run with `pytest -x` use:
+#
+#   ./run-integration-tests.sh -e py35 -- -x
+
+cargo build -p deltachat_ffi --release
+
+# CFLAGS=-I`pwd`/deltachat-ffi
+# LD_LIBRARY_PATH=`pwd`/target/release
+# export CFLAGS
+# export LD_LIBRARY_PATH
+export DCC_RS_DEV=$(pwd)
+
+pushd python
+toxargs="$@"
+if [ -e liveconfig ]; then
+    toxargs="--liveconfig liveconfig $@"
+fi
+tox $toxargs
+ret=$?
+popd
+exit $ret