add logrus template.

[trusch]

This adds a template similar to the log template but uses logrus with field annotations for

• component (name of the interface)
• method
• parameters
• results

This makes it easier to retrieve these values out of the structured output of logrus' formats.

[coveralls]

Pull Request Test Coverage Report for Build 14

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 93.365%

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Totals
Change from base Build 12:	0.0%
Covered Lines:	197
Relevant Lines:	211

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💛 - Coveralls

[hexdigest]

HI, @trusch

First of all thank you for your PR!

Here are my thoughs:

1. I think in case of logrus it makes sence to pass logrus.Entry as a parameter to the constructor. This will allow users to configure whatever way they want.
2. I think that it makes sence to use logrus.Error/logrus.Errorf methods in case of errors, please check {{$method.ReturnsError}} section in the original "log" template
3. Please generate decorator with your new template for the TestInterface (templates_tests/interface.go). So that we can be sure that generated code is valid.
4. Also I notices incorrect comment for the constructor (which is my bad and I'll fix it in the "log" template). It should be something like:

  // New{{$decorator}} instruments an implementation of the {{.Interface.Type}} with logrus logger

Do you have time to fix above issues?

[hexdigest]

@trusch Can you please check the logrus template I just added? What would you add/change?

[trusch]

@hexdigest looks good to me! Thank you very much for this template and the project in general!