NTLM authentication adds a dependency even if you don't need it

[jenkin]

It's the pip package requests_ntlm. I'm using Python 2.7.3 on Debian 7.11. Maybe you can import the ntlm module only if the ELASTICSEARCH_AUTH parameters has NTLM value?

[jsgervais]

I'm not sure it can be done if some parameters have some values, however, I think you can import a package when it's available with precompiling conditions and then assert in the code if it is available.

[jayzeng]

Looks like I can use extra_require in setup tools (https://setuptools.readthedocs.io/en/latest/setuptools.html#declaring-extras-optional-features-with-their-own-dependencies), let me play around it

[jayzeng]

#47

[jayzeng]

@jenkin @jsgervais I made the changes and pushed a build to pypi, will be great if you guys can give it a test.

[jayzeng]

Going to close this issue, please re-open if it doesn't work.