Re-introduce caching of TimeRE and compiled regexes with added thread-safety.

Also remove now unnecessary property attributes for thread safety
(no longer have lazy attributes) and code simplicity reasons.

Timezone storage has been reworked to be simpler and more flexible.  All values
in LocaleTime instances are lower-cased.  This is all done to simplify the
module.

The module now assumes nothing beyond the strptime function will be exposed for
general use beyond providing functionality for strptime.

Author: brettcannon