Add --postinst-commands option

```
$ rm -rf debian; make-deb --no-test --python=/usr/bin/python3 --python-version=3.5 --postinst-commands='mkdir -p /var/log/sm'
'debian' directory successfully placed at the root of your repository

$ cat debian/smbot.postinst
#!/bin/sh

#DEBHELPER#

mkdir -p /var/log/sm
```

bin/make-deb

@@ -33,13 +33,17 @@ def get_dh_virtualenv_options(python, test):
 @click.option('--test/--no-test',
               default=True,
               help='Whether to run python setup.py test')
-def main(python, python_version, test):
+@click.option('--postinst-commands',
+              default=None,
+              help='Commands to put in postinst script')
+def main(python, python_version, test, postinst_commands):
     dh_virtualenv_options = get_dh_virtualenv_options(python, test)
     try:
         debconf = DebianConfiguration(
             os.getcwd(),
             python_version=python_version,
             dh_virtualenv_options=dh_virtualenv_options,
+            postinst_commands=postinst_commands,
         )
         debconf.render()
     except DebianConfigurationException as e:

make_deb/__init__.py

@@ -32,7 +32,9 @@ class DebianConfiguration(object):
         "compat": 9,
     }
 
-    def __init__(self, rootdir, python_version='2.x', dh_virtualenv_options=None):
+    def __init__(self, rootdir,
+                 python_version='2.x', dh_virtualenv_options=None,
+                 postinst_commands=None):
         self.rootdir = rootdir
         self.context = self.DEFAULT_CONTEXT.copy()
         self.context.update({"date": datetime.datetime.now()})
@@ -47,6 +49,7 @@ def __init__(self, rootdir, python_version='2.x', dh_virtualenv_options=None):
                 "pre_depends_python": "python2.7-minimal | python2.6-minimal"})
         self.context.update({"python_version": python_version})
         self.context.update({"dh_virtualenv_options": dh_virtualenv_options})
+        self.context.update({"postinst_commands": postinst_commands})
 
     def _context_from_git(self):
         try:
@@ -117,3 +120,12 @@ def render(self):
         trigger_filename = "%s.triggers" % self.context['name']
         with open(os.path.join(output_dir, trigger_filename), "w") as f:
             f.write(trigger_content+"\n")
+
+        trigger_content = Template(
+            resource_string("make_deb", "resources/debian/postinst.j2").
+            decode('utf-8')
+        ).render(self.context)
+
+        trigger_filename = "%s.postinst" % self.context['name']
+        with open(os.path.join(output_dir, trigger_filename), "w") as f:
+            f.write(trigger_content+"\n")

make_deb/resources/debian/postinst.j2

@@ -0,0 +1,5 @@
+#!/bin/sh
+
+#DEBHELPER#
+
+{{ postinst_commands }}