Feature/testing vic5

[jhamman]

This is the start of the VIC test module.

Notable Features

1. Travis is now compiling using gcc and clang, builds are passing for both compilers.
2. All tests are run from the run_tests.py script.
3. No changes were made to the VIC source code
4. The directory tests/test_data/will not be included in the repository but is available for preview here. I'm still adding a few pieces to this but the general structure is now in place.
5. Currently, the system tests are the most built out but with the test structure I've put together, more can be easily added.

Test Module Structure:

1. unit: function level tests.
2. system: tests that aim to address model runtime issues. These tests are generally very quick.

• configuration errors - tests that address model startup and error checking.
• restart: tests that address model state and restart capacity.
• I/O: tests that address model input and output functionality.
  • forcings come out the way the come in
  • parameter files are appropriately read in allocated.

3. science: tests that aim to assess the model's scientific skill. Many of these tests are compared to observations of some kind.
4. examples: a set of examples that users may download and run.
5. release: longer, full domain simulations performed prior to release demonstrating model output for a final release.

Areas in need of further development:

• Science Tests: comparisons with observations
• Image Mode Driver Tests: currently all tests use the classic driver
• Standard test comparing image and classic drivers.
• Tests datasets for lesser used options:
  • Blowing snow,
  • Precipitation correction,
  • Lakes and wetlands, and
  • Carbon cycle.

This could be merged now or we could wait until we've added more tests. Since there are no changes to the source code of VIC, the only downside to merging now is that there will need to be more pull requests in the future.

fixes #79.

[bartnijssen]

No code review at this stage, but will accept pull request to get this started and since it lives in its own directories