Update function call of add_computed_field

[cschloer]

The add_computed_field function in data flow (https://github.com/datahq/dataflows/blob/master/dataflows/processors/add_computed_field.py#L73) looks like this:

def add_computed_field(*args, resources=None, **kw):

but the add_computed_field processor in datapackage_pipelines calls it like this:

def flow(parameters):
    return Flow(
        add_computed_field(
            parameters.get('fields', []),
            parameters.get('resources')
        ),
)

This PR correctly calls the add_computed_field flow using resource as a named parameter. Without this PR the add_computed_field processor does not work.

The function signature in dataflows was updated sometime between 0.0.44 and 0.0.48 but the function in datapackage_pipelines was not updated.

[akariv]

Thanks for reporting and fixing @cschloer !

I will make sure tests pass and then I'll merge the PR.

[coveralls]

Pull Request Test Coverage Report for Build 1041

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+8.5%) to 25.473%

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Totals
Change from base Build 1040:	8.5%
Covered Lines:	1698
Relevant Lines:	6666

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💛 - Coveralls