Gama

Add a ``goal`` hyperparameter that can be used to let GAMA configure the AutoML hyperparameter based on user intent.

Bugfixes:
- `predict_proba_arff` now also accepts a `target_column` as expected from the previous update.

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Features:
- `gama.__version__` can now be used to retrieve gama's version.
- `fit_arff`, `score_arff` and `predict_arff` now accept a `target_column` parameter to specify the target.
If left unset, the last column of the ARFF file is assumed to be the target column.

Bugfixes:
- fit(x, y) may now be called with y as (N,1) array.
- ensemble post-processing is now compatible with non-zero indexed class labels

Maintenance:
- `__version__.py` is now the only place with hard-coded version.

This is the first release of 2019. Decided to go with [YY.0M.MICRO](https://calver.org/) format for versioning.
Reason: Creating a release for archiving through zenodo for the JOSS paper.
Changes: No previous release.

This is a release specific for integration with the D3M ecosystem. Do not use this release unless you know what you are doing.