Add isatty() method to PythonQtStdIn class

[fepegar]

Resolves #48.

Context: Slicer/Slicer#5705.

[lassoan]

This looks good to me, but it would be better if you added a bool _isatty{false} member to PythonQtStdInRedirect and return the value of this in isatty(). This would allow using this class to stream input from an interactive terminal.

[fepegar]

Thanks for reviewing, @lassoan.

added a bool _isatty{false} member to PythonQtStdInRedirect

Sorry, I don't know how to do that. I don't know much C++.

[lassoan]

@fepegar I could not update your pull request, so created a new one: #50

I've tested it in Slicer and verified that light-the-torch package can be installed and imported correctly.

[fepegar]

Great! Thanks, @lassoan. I see what you mean by adding a new member. It wasn't that hard! Next time I'll know what to do.