Node buildpack updated to circumvent npm cert issues

Change effective on 28 February 2014

A change was recently made to npm’s infrastructure that caused many users to receive a SELF_SIGNED_CERT_IN_CHAIN error during installation and publishing of packages. The npm-recommended fix is to set a blank value for ca in your npm config.

This issue can be circumvented by upgrading to node 0.10.26 or greater, but the upgrade is not required. The node buildpack has been updated to automatically generate an .npmrc for your app with the blank ca entry, if one is not already present.