add clean script

scripts/clean.sh

@@ -0,0 +1,19 @@
+#!/bin/sh -e
+PACKAGE="orm"
+if [ -d 'dist' ] ; then
+    rm -r dist
+fi
+if [ -d 'site' ] ; then
+    rm -r site
+fi
+if [ -d 'htmlcov' ] ; then
+    rm -r htmlcov
+fi
+if [ -d "${PACKAGE}.egg-info" ] ; then
+    rm -r "${PACKAGE}.egg-info"
+fi
+find ${PACKAGE} -type f -name "*.py[co]" -delete
+find ${PACKAGE} -type d -name __pycache__ -delete
+
+find tests -type f -name "*.py[co]" -delete
+find tests -type d -name __pycache__ -delete