Prevent error msg for loading biom files without .biom suffix

Addresses #63
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
Update scripts/normalize_by_copy_number.py

avoid naked raise statement.
Merge pull request #67 from mlangill/tutorial_files

Update genome and metagenome prediction tutorials
Merge pull request #65 from mlangill/issue63

Prevent error msg for loading biom files without .biom suffix