Rewrite get_qiime_scripts_dir

Now runs the equivalent of 'which print_qiime_config.py' to infer the scripts directory.
update util.py modules, update some unit tests
update print_qiime_config.py and parallel scripts
update workflow library code
update denoiser code and add qiime.util.which

qiime.util.which is now my favorite python function
remove remaining refs to python_exe_fp
Update docs with config file changes
remove cloud_environment from QIIME
Remove working_dir from QIIME

temp_dir (in QIIME config) is now used in place of working_dir (should only affect some pieces of parallel QIIME).
Remove poller_example.py

This has been slated for removal for awhile... it's time
remove poller_fp option lookup

not being used anywhere
Merge pull request #1342 from jrrideout/issue-1338

Remove qiime_scripts_dir and python_exe_fp
print_qiime_config.py mpl version check handles rc

The version check for matplotlib that is performed in print_qiime_config.py now handles version strings that end in ```rc```. For example, ```1.1.1rc``` now passes the version check instead of throwing a ```ValueError``` when casting the last element to an integer.

Ran into this issue when testing out a QIIME installation that had mpl 1.1.1rc installed.
Fix test_stats.py floating point test failure

Partially addresses #1347.
Typo

s/agsint/against/
Merge pull request #1345 from jrrideout/mpl-version-check-fix

print_qiime_config.py mpl version check handles rc
Merge pull request #1348 from jrrideout/test-num-issues

Fix test_stats.py floating point test failure
Merge pull request #1349 from frederic-mahe/patch-1

Typo