Bugfix: Filter out linters that are disabled in the configuration.

[peret]

Fixes #531.

The getLinter() function just passes on the linter config (if it's an object), or continues with an empty object if it's any other values. This leads to unexpected behavior when setting a specific linter to false in the config. I.e. the linter is not disabled, as one would expect, but an empty linter configuration is used.

This PR fixes the issue by explicitly filtering linter configs that are false before passing them on to getLinter().

• The build passes
• TSLint is mostly happy
• Prettier has been run

[wingrunr21]

Thanks. This was on my list to look into this weekend but you beat me to it!