Clean up .gitignore

Moving subdirectory gitignores in here makes it possible for tools that
use gitignore files (like ag[1]) to ignore those directories when
searching through the code.

[1]: https://github.com/ggreer/the_silver_searcher
preamble: Don't double-dev things.

When the version in package.json is X.Y.Z-dev, we were generating
version strings like X.Y.Z-dev-dev-abcdef123
Clean up stray comment characters
Make push_next tool use awscli