Add .json file ending to leveldown package

[PascalTemel]

The missing file ending resulted in build issues in our project.

[ralphtheninja]

Thanks!

1.3.5 (yeah managed to release 1.3.4 before merging, doh)

@juliangruber You might want to rebase your clean up branches

[juliangruber]

.json is one of the default file ending that nodejs tries when requiring a file without one, you can verify so be going to a module and disk and running this:

$ node -pe "require('./package')"

So I don't know what the issue in your build process really was, but if everything works like node or browserify - which this module targets as environments - it should work.

Did you maybe use something like webpack?

[PascalTemel]

@juliangruber I'm sorry, apparently I missed the notification. levelup came as a dependency of pouchdb / worker-pouch. It's an angular2 project and our build process consists of NGC -> rollup -> closure