add tox to the tree for doing bashate checking

this enables a bashate rule for doing style checking. Fixes for
issues found will come in a second patch so any rules that people
want ignored could be debated there.

Change-Id: I7dffa587784297ec65596a36c0600473cfa591c6

test-requirements.txt

@@ -0,0 +1 @@
+bashate>=0.2

tox.ini

@@ -0,0 +1,13 @@
+[tox]
+envlist = bashate
+minversion = 1.6
+skipsdist = True
+
+[testenv]
+install_command = pip install -U {opts} {packages}
+setenv = VIRTUAL_ENV={envdir}
+deps = -r{toxinidir}/test-requirements.txt
+
+[testenv:bashate]
+commands =
+  bash -c "ls *.sh | xargs bashate -v {posargs}"