properly parse NO_SSL env var (#126)

Bug fix:
The default for `NO_SSL` environment variable is `False`.
When the actual value, in runtime, is `True`, the code "ignores" it.
The reason: the code does not parse the given string. So it evaluates a non empty string as "True".
To resolve this, the suggested code parses the given string to a boolean value.

snappass/main.py

@@ -9,8 +9,9 @@
 from redis.exceptions import ConnectionError
 from werkzeug.urls import url_quote_plus
 from werkzeug.urls import url_unquote_plus
+from distutils.util import strtobool
 
-NO_SSL = os.environ.get('NO_SSL', False)
+NO_SSL = bool(strtobool(os.environ.get('NO_SSL', 'False')))
 URL_PREFIX = os.environ.get('URL_PREFIX', None)
 TOKEN_SEPARATOR = '~'