Closes #10 Adding vars as a template_field to DbtBaseOperator

[marcusintrohive]

Adding vars to the list of template_fields on the DbtBaseOperator.

This will allow passing variables to the operator from the dag_run.conf

[codecov]

Codecov Report

Merging #41 (d6b8e9e) into master (fc0a12f) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master      #41   +/-   ##
=======================================
  Coverage   97.34%   97.34%           
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  Files           5        5           
  Lines         677      677           
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  Hits          659      659           
  Misses         18       18           

Flag	Coverage Δ
unittests	97.34% <ø> (ø)

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Impacted Files	Coverage Δ
airflow_dbt_python/operators/dbt.py	99.32% <ø> (ø)

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[tomasfarias]

Looks good to me, let's wait and see what the tests say before merging. I'll probably push this out in version 0.12, and leave the custom backend code for 0.13 (as that is a much bigger and riskier change).

Important to note that this probably doesn't work with Airflow 1.x or 2.0 as support for Jinja's NativeEnvironmentwas added in 2.1, and we expect vars to already be a dict. Eventually, we can work that in a different issue.

[marcusintrohive]

Thanks @tomasfarias!