Fix lodash.omit import

[dariusk]

It looks like via typo this module had accidentally been loading omit via lodash (the full lodash package itself, which is not included in package.json but is in the dependency tree elsewhere) and not via lodash.omit that is actually a dependency in package.json. This was causing some problems in downstream dependencies. Basically the full lodash package is available to this particular project via a string of devDependencies so the package builds just fine and even distributes fine, but if a downstream project does not have lodash anywhere in its dependencies it will break (since the devDependencies aren't distributed with the release).

This PR adds the @types needed for lodash.omit and changes the code to import lodash.omit itself.