updated to ignore files created by compiling denoiser code
ported downstream workflow functions to downstream.py

this is really bloated right now with extra test data and imports. will be cleaned up from here.
modified to split workflow function to new script

still needs some clean-up
fixed missing import
updated to use new test data
removed unused imports
removed extra import
updated all tests to use qiime.test.get_test_data_fps()
updated imports and credits
cleaned up comments and credits