Make scrape_help.py work in Python 3
Fix scrape_help.py with no arguments in Python 3
Generate rst files for the commands
Remove old command docs
scrape_help.py: Generate help for conda-build commands
Generate command help in the Makefile
Add a metapackage recipe for the docs build dependencies
Update README and .travis.yml with conda-docs-deps metapackage
Add a note about the conda-docs-deps conda package on Windows
Add build-commands index file

This is needed for the "next" buttons to work correctly.
Use concurrent.futures to generate manpages in parallel
Add note about needing conda-build to be installed
Install conda-build in Travis for the docs
Try disabling concurrency in scrape_help.py to see if it build in Travis
Use list(executor.map) in scrape_help.py

This ensures that any exception raised is not silenced.
Workaround feature needed in unreleased version of conda for Travis
Add Sphinx references for the commands

This makes the docs build without any errors or warnings.
Merge pull request #24 from asmeurer/command-docs

Command docs