Add classes for authentication methods
Rename AuthenticationMethod to Authenticator
More authentication work. I'm not sure I like how multi-factor authentication is going...
Ah well, I'm just going to do it like this for now...

SSHFileSystem.connect now supports authentication using
Authenticator instances.
A bit more documentation
Initial FTP implementation
More FTP work
Python 3 compatibility fixes

Fileutils can now be imported from a Python 3 interpreter! Basic
functionality in fileutils.local appears to be working. Haven't
yet tested SSHFile or URL.
Merge commit '33ceed2e6846552f180dfdaa821efe84317e86cd'

Conflicts:
	projects/fileutils/fileutils/ftp.py
	projects/fileutils/fileutils/local.py
	projects/fileutils/fileutils/ssh.py
	projects/fileutils/fileutils/url.py
Figures I'd miss something...
More Python 3 fixes. Basic local, SSH, and URL file operations seem to work.
Initial skeleton .travis.yml file
Initial unit tests. These only test (part of) fileutils.local right now.
Split 'projects/fileutils/' into commit 'a23fd822c85b54fc814c85a0c60bbc6fbe4db4b4'

git-subtree-dir: projects/fileutils
git-subtree-mainline: 3de8946059bc80131514040a244d6e8c33bfbc08
git-subtree-split: a23fd822c85b54fc814c85a0c60bbc6fbe4db4b4