don't require minitest/autorun in lib file
The README indicates that these methods should be non-descructive...

...but the current implementation will mutate a Hash in-place for nested
hashes. This commit fixes that issue. However, the implementation is not
very efficient (will address that in a subsequent commit).
simplified implementation of symogriform
simplified implementation of hashmogrify
Merge pull request #1 from dtao/master

several suggested improvements to symogriform and hashmogrify