Add tutorial files to github repository.

Addresses #35
Update metagenome prediction tutorial

Addresses #36
Allow creation of recursive directories for output
Change ancestral_state_reconstruction.py to use 'ace_pic' as default asr method.

Since PICRUSt uses 'ace_pic' method for producing precalculated files, the asr method should be set to the same default.
Change heading from 'metagenome prediction' to 'metagenome prediction tutorial'
Update genome prediction tutorial

Addresses #39
Merge pull request #67 from mlangill/tutorial_files

Update genome and metagenome prediction tutorials