fix for issue #37

this addresses issue #37, but required that we move the data directory under the picrust library directory and reference it as package data in setup.py. this allows references to those files (e.g., in normalize_by_copy_number.py) to work when the user has installed PICRUSt with setup.py or by just adding the library code directory to their $PYTHONPATH.
added support_files to package_data

this will allow these files to be accessible even if PICRUSt is installed with setup.py.
updated default path to adhere to new location of data files
updated default path to input_count_table to reflect new location of this file
Merge pull request #38 from gregcaporaso/issue-37

fix for issue 37