Add Timezone to query to fix Aggregation issue

[farzadpanahi]

Right now the generated query does not include timezone. When timezone is not included, Kairosdb will assume default timezone UTC which will cause some unexpected results in queries that are timezone related like Aggregation with SAMPLING option set.

For instance if you are doing an aggregation with SAMPLING true with 1 DAY range, then if timezone is not sent the beginning of the range which will be time 0:00 of each day will be based on UTC timezone, rather than browser's timezone. This will cause unexpected results because the range window is shifted.