Merge pull request #3 from pat/feature/default-params

Adding the ability to set default parameters.
Bump version to 1.2.0. Update CHANGELOG.
Forecast::IO is now ForecastIO.

This avoids namespacing issues with other projects (e.g. Rails apps) with classes called Forecast.

Forgot the IO suffix in version file.

Merge fix.

Updating new docs with new namespace.