upgrade npm to 3.3.12

Please find enclosed:

1. A fix for some of the ENOENT issues people see when updating modules that have bundled dependencies that are invalid according to the included package.json.
2. An important fix to how partial shrinkwraps are handled. This is an underspecified and undocumented feature that a few popular modules take advantage of.
3. A fix for crashes on non-object bin fields in package information returned from some third party registries. (npm's registry does not return non-object bin fields due to normalization of that field and others during publication.)

As always, the full details are available in our changelog.

r: @Fishrock123 r: @chrisdickinson