idea: asset-size report for just the core of the library

[runspired]

Because we conditionally remove code that exists to support specific legacy packages (notably model/adapter/serializer) the reported size of store which represents the essential core of ember-data is over-reported. As we work to rationalize the network layer this over-reporting will become even more substantial. It is already likely close to 30% of the reported size of store, and as we continue to deprecate the legacy model world it's likely this number grows as high as 70%.

We should build a tiny package that just installs the store package (the only essential package at this point) and reports it's size. Since most folks will likely choose to use our cache as well we should probably build a similar scenario for those two packages.