Add weekrange subcommand
Add weekrange subcommand help
Fix first week to ISO standard and add tests
Update filter to simple week check
Merge branch 'develop' into feature/issue-11-add-week-range-to-daterange-subcommand

Fixed Conflicts:
	README.rst
	gdt/tests/test_gdt.py
Hold clarification on week 1 status
Fix test and clarify week one for strftime
Update docs
Merge pull request #11 from praekelt/feature/issue-11-add-week-range-to-daterange-subcommand

Add week range to daterange subcommand