Remove 'api' attr from swagger definition

[mits87]

Fix the problem with not necessary api attribute inside the swaggerDefinition file:
Issue: #233

[kalinchernev]

@mits87 thanks for taking the time to fix this! The pull request is ok, only 1 request: please update the documentation as briefly mentioned at #233 (comment)

lastly, a small doc update to remove the apis mention from https://github.com/Surnet/swagger-jsdoc/blob/master/docs/CLI.md#definition-file and remove When you don't want to or can't pass apis from the definition above, specify like following:

[mits87]

@kalinchernev Done

[kalinchernev]

@mits87 thank you!