CLIMATE-475 - Fix metric imports in ocw.tests.test_metrics

- Remove explicit metric class imports from ocw.metrics so the import
  list doesn't become insanely long and unwieldy. Metrics now need to
  reference 'metrics' when they're called throughout the tests.
CLIMATE-477 - Add nose-exclude to Easy OCW pip install
CLIMATE-476 - Add __str__ implementation to Dataset
CLIMATE-476 - Add __str__ implementation to Bounds
CLIMATE-476 - Add __str__ implementation to Evaluation
Add check for existing ocw virtualenv
Merge branch 'CLIMATE-441'

- Fixes PR#80
Merge branch 'CLIMATE-476'

- Closes PR#79
Resolve CLIMATE-477. Merge PR #78.
Resolve CLIMATE-475. Merge PR #77.
Update dataset_processor function parameter documentation

- Update the dataset_processor function documentation so the references to
  ocw.dataset.Dataset objects are in a consistent form. In the future,
  these should be updated to properly reference the Dataset object's
  documentation (if possible).
Update data_source.local function parameter documentation

- Update the data_source.local function documentation so the references to
  ocw.dataset.Dataset objects are in a consistent form. In the future,
  these should be updated to properly reference the Dataset object's
  documentation (if possible).
Update data_source.rcmed function parameter documentation

- Update the data_source.rcmed function documentation so the references to
  ocw.dataset.Dataset objects are in a consistent form. In the future,
  these should be updated to properly reference the Dataset object's
  documentation (if possible).
Update metrics function parameter documentation

- Update the metrics function documentation so the references to
  ocw.dataset.Dataset objects are in a consistent form. In the future,
  these should be updated to properly reference the Dataset object's
  documentation (if possible).
- Minor documentation changes for clarity.
Update utils function parameter documentation

- Update the utils function documentation so the references to
  ocw.dataset.Dataset objects are in a consistent form. In the future,
  these should be updated to properly reference the Dataset object's
  documentation (if possible).
- Minor documentation changes and rewordings for clarity.
Resolve CLIMATE-479. Merge PR #81.
CLIMATE-404, Open Climate Workbench Command Line tool

This is command line tool that uses OCW API
and lets user to upload a local model file, pick
an observation to run metrics and get resutls as plots.
Right now it just accepts one model and one observation
and can run Bias as metric.
Minor typo fix in README
Merge branch 'CLIMATE-403', Resolved CLIMATE-404, Merge PR #82.