Merge pull request #1 from xDAGRONx/master

Accept any Date-like object
Add optional start day to initialize

If a valid day is given, it will be used in place of the start day
defined on the class. If not given, or if an invalid day is given, the
default will be used.
Add examples to README for optional start_day

Add examples demonstrating the ability to optionally pass in a start
day to the constructor.
Merge branch 'optional-start-day' of github.com:thermaldonkey/ordered_week into optional-start-day