Making Isca conda-installable

[dennissergeev]

Given the success of running Isca with conda libraries (as first done by @spencerahill in #108 ), it looks like it's possible to make the model itself conda-installable. Even if there is a performance hit as @sit23 pointed out (remains to be tested), it would be still useful.

I made a separate environment on my Ubuntu machine by installing all the libraries from the conda-forge channel and Isca indeed seems to run fine, at least the Held-Suarez test.

The next necessary step to making Isca available via conda is continuous integration (CI) with automated tests. As a proof of concept, I connected my Isca fork to Travis CI. Travis uses the conda environment mentioned above to install everything and then runs a test in the tests/ directory using pytest.

If this is useful, I'll create a PR or a branch for this development.