integrations: add integration support

* added db migration for integration table, version 55
* added integrations views/templates/models
* added slack integration
* added h.url.current() support for pyramid only contexts
* added issues extractor for commit messages
* renamed repo-deleted/repo-created to repo-delete/repo-create
* removed marshmallow
* added serialization for events to static dicts of data
* added lazy_ugettext for translation of start time string

setup.py

@@ -78,7 +78,6 @@ requirements = [
     'ipython',
     'iso8601',
     'kombu',
-    'marshmallow',
     'msgpack-python',
     'packaging',
     'psycopg2',