Updating ThermoML dataset section of README.md to clarify format vs source issues

[davidlmobley]

Clarifying that a ThermoMLDataset provides access to a dataset in the ThermoML format, even if it does not come from the ThermoML archive proper, as originally I didn't understand this point.

[jchodera]

Looks good. Maybe we can extend this to provide a few different ways to pull in ThermoML files?

(This is just some brainstorming.)

• Pull in a single ThermoMLDataset from the ThermoML Archive via its DOI:

dataset = ThermoMLDataset(keys='10.1016/j.jct.2005.03.012')

• Retrieve multiple datasets from the ThermoML archive:

thermoml_keys = ['10.1021/acs.jced.5b00365', '10.1021/acs.jced.5b00474']
dataset = ThermoMLDataset(keys=thermoml_keys)

• Grab all ThermoML files from a different URL

dataset = ThermoMLDataset(url='http://openforcefieldgroup.org/thermoml-datasets')

• Grab data from a local path

dataset = ThermoMLDataset(url='file:///Users/choderaj/thermoml')

• Grab a specific DOI from a different URL

dataset = ThermoMLDataset(keys=['10.1021/acs.jced.5b00365', '10.1021/acs.jced.5b00474'], url='http://openforcefieldgroup.org/thermoml-datasets')

• Grab data from the ThermoML and also from another URL

dataset = ThermoMLDataset(keys=thermoml_keys)
dataset.retrieve(keys=local_keys, url='http://openforcefieldgroup.org/thermoml-datasets')

[davidlmobley]

@jchodera - that looks good to me. Did you want me to put this into the README.md as well?

[jchodera]

@jchodera - that looks good to me. Did you want me to put this into the README.md as well?

Yes, but please tweak if you think of more use cases or a better API.