Add texttable to requirements.txt

requirements.txt

@@ -1,3 +1,4 @@
 git+git://github.com/dotcloud/docker-py.git@5c928dcab51a276f421a36d584c37b745b3b9a3d
 docopt==0.6.1
 PyYAML==3.10
+texttable==0.8.1