Add meta options to logging and error logging.

[conradoqg]

Organizes the Readme.md, puts logging before error logging and separate logging options from error logging options.

Add baseMeta and metaField to better control how meta is send to winston, allowing better logging features when using external logger as loggly. Corrects minor typo in test-coverage script command at package.json. Add tests for the metaField option.

[floatingLomas]

So this allows you to define meta constants that get included with every log message, and to also allow moving the response data from the original meta to a specific property within the meta?

[conradoqg]

Yes for both. Sorry for my English.

[thecatontheflat]

Thank you. This PR actually helped me to understand the configuration better

[bithavoc]

Thank you @conradoqg