Allow configuration with unordered range hashes

We should be more amenable to valid hashes that are simply not in the
right order when passed into the configuration.
Allow holidays to be configured with array-like objects

In my case, I'd like to provide a set of holidays directly to the gem.
There's no functional reason not to be flexible in this case as long as
the input can be successfully converted into an array at processing
time.
Merge pull request #10 from craiglittle/relax-config-checks

Relax configuration input formats