[0.2.dev0] Template for loading data

[smmaurer]

This PR adds the initial chunk of data i/o functionality, as described in issue #66.

New template: urbansim_templates.io.TableFromDisk()

Template for registering data tables from csv or h5 files, to replace datasources.py. See docstrings and sphinx file for full documentation, which will appear online after this PR is merged.

Basic usage: Create an instance of the template class and set some properties (table name, file type, path, etc). "Registering" with ModelManager saves the object to disk and creates an Orca step with instructions to set up a table. "Running" the object/step registers the Orca table. Data is read from disk lazily when it's needed.

New standard template property: autorun

When you register a template instance with ModelManager, it now checks for a property called autorun. If it's present and True, ModelManager will immediately "run" the step.

This will be helpful for preparatory logic like this new template: If you have some table-loading steps defined in your configs directory, the tables will automatically be registered with Orca when you initialize a ModelManager session.

Data validation

The new template includes a validate() method that checks some basic expectations about the data that's being loaded:

• contains a unique index (or multi-index)
• if it contains columns whose names match the indexes of previously registered tables, checks whether they make sense as join keys
• performs the same check for columns of previously registered tables whose names match the index of the new table

This gets us much of the way to either (a) automatically generating Orca "broadcasts" between tables or (b) performing table merges without needing broadcasts. See issue #78 for more on this.

Versioning

0.2.dev0

To do before merging

• implement and test h5 features
• finish documentation
• update changelog
• finalize versioning

[coveralls]

Coverage decreased (-0.06%) to 88.843% when pulling 9409d2f on data-loading into 1a5f2bf on master.