Add datetimetz module for timezone information in date display

Allow multiple comma seperated timezones

Handle click to cycle through configured timezones
Example:
```
bumblebee-status -m datetimetz -p \
datetimetz.timezone=\
"Australia/Sydney,Pacific/Auckland,America/Los_Angeles"
```
Added dependencies to travis config

bumblebee/modules/datetimetz.py

@@ -0,0 +1,79 @@
+# pylint: disable=C0111,R0903
+
+"""Displays the current date and time with timezone options.
+
+Parameters:
+    * datetimetz.format   : strftime()-compatible formatting string
+    * datetimetz.timezone : IANA timezone name
+    * datetz.format       : alias for datetimetz.format
+    * timetz.format       : alias for datetimetz.format
+    * timetz.timezone     : alias for datetimetz.timezone
+    * datetimetz.locale   : locale to use rather than the system default
+    * datetz.locale       : alias for datetimetz.locale
+    * timetz.locale       : alias for datetimetz.locale
+    * timetz.timezone     : alias for datetimetz.timezone
+"""
+
+from __future__ import absolute_import
+import datetime
+import locale
+import pytz
+import tzlocal
+import bumblebee.input
+import bumblebee.output
+import bumblebee.engine
+
+ALIASES = ["datetz", "timetz"]
+
+def default_format(module):
+    default = "%x %X %Z"
+    if module == "datetz":
+        default = "%x %Z"
+    if module == "timetz":
+        default = "%X %Z"
+    return default
+
+class Module(bumblebee.engine.Module):
+    def __init__(self, engine, config):
+        super(Module, self).__init__(engine, config,
+            bumblebee.output.Widget(full_text=self.get_time))
+        engine.input.register_callback(self, button=bumblebee.input.LEFT_MOUSE, cmd=self.next_tz)
+        engine.input.register_callback(self, button=bumblebee.input.RIGHT_MOUSE, cmd=self.prev_tz)
+        self._fmt = self.parameter("format", default_format(self.name))
+        self._timezones = self.parameter("timezone", tzlocal.get_localzone().zone).split(",")
+        self._current_tz = 0
+
+        l = locale.getdefaultlocale()
+        if not l or l == (None, None):
+            l = ('en_US', 'UTF-8')
+        lcl = self.parameter("locale", ".".join(l))
+        try:
+            locale.setlocale(locale.LC_TIME, lcl.split("."))
+        except Exception:
+            locale.setlocale(locale.LC_TIME, ('en_US', 'UTF-8'))
+
+    def get_time(self, widget):
+        try:
+            tz = pytz.timezone(self._timezones[self._current_tz].strip())
+            retval = datetime.datetime.now(tz=tzlocal.get_localzone()).astimezone(tz).strftime(self._fmt)
+        except pytz.exceptions.UnknownTimeZoneError:
+            retval = "[Unknown timezone: {}]".format(self._timezones[self._current_tz].strip())
+
+        enc = locale.getpreferredencoding()
+        if hasattr(retval, "decode"):
+            return retval.decode(enc)
+        return retval
+
+    def next_tz(self, event):
+        next_timezone = self._current_tz + 1
+        if next_timezone >= len(self._timezones):
+            next_timezone = 0     # wraparound
+        self._current_tz = next_timezone
+
+    def prev_tz(self, event):
+        previous_timezone = self._current_tz - 1
+        if previous_timezone < 0:
+            previous_timezone = 0     # wraparound
+        self._current_tz = previous_timezone
+
+# vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4