ENH: Add classes for CommandLine interfaces with input passed via env or stdin

[ashgillman]

trafficstars

Adds StdInCommandLine and EnvironmentInputCommandLine

What is this?

I have implemented this for some custom Interfaces that I have had to create. They wrapped scripts that either took inputs as environment variables, or were interactive scripts that prompted the user and asked for input via stdin.

I included a basic test case (using sed the stream editor) to demonstrate how they are used.

I'm interested to hear what the maintainers think about these changes, since they don't actually support any of the Interfaces within Nipype. I am currently just maintaining the changes in parallel to development.

[ashgillman]

Comments/criticisms welcome