conda install --use-local slycot

[kangwonlee]

• This PR intends to repair conda install cannot install from local #41 conda install --override-channels -c local slycot being unable to find the local slycot for python 2.7 && TEST_CONDA=1.
• After this change, the build could find the local slycotbut one or two of tests still may fail.
• Please see if this makes the code more harmonious.

[roryyorke]

Thanks for this contribution.

I think the problem this addresses is fixed in d23ab7b, and Travis CI is now passing. I used "local::slycot" instead of "--use-local slycot"; the "channel::package" form is not well-documented, but seems more explicit about where the package will come from.

[kangwonlee]

Thanks for d23ab7b and the comment. conda install <channel>::<package> seems interesting, too.