allow caching of all objects by time period

[ahwagner]

CIViCpy should, by default, timestamp civicrecord objects. There should be routines for storing and loading civicrecord objects, and checks should be made based off of a global timedelta value (which should be loaded in __init__.py).

Bonus points for:

• Adding a .conf file where this may be set
• Properly caching these records on load
• Creating flags to auto-update / auto-ignore expired records when saving / loading
• Checking for file cache before expensive calls to obtain all variants / genes