use datetime.strptime instead of parser

its much faster and we're always parsing ISO 8601 format
fix tests
fix the other tests too

To handle ISO 8601
one more test change

this isn't a great test change, but zulu is implied in 8601
Merge pull request #38 from joshowen/master

use datetime.strptime instead of parser
Merge branch 'master' of https://github.com/tempodb/tempodb-python into python3

Conflicts:
	tests/base/datapoint_tests.py
	tests/client/tests.py
s/unittest2/unittest/g