Private Key public?

[Aypac]

This example has the private key in the "public" js file. I don't think this is good for production (and so do others: https://groups.google.com/forum/#!searchin/freesound-api/javascript/freesound-api/7DdxIx5FggU/6D0xnvxKK2kJ ). There should be a mention of this in the readme, together with possibilities to circumvent this. Maybe we could also introduce a php-file working as a specific proxy for this purpose? Or would that not fit this repo?