internal/blobstore, internal/multihash: new packages
internal/blobstore: new package

	This currently layers on top of juju/blobstore,
		but is designed so that it is easy to swap out
			that backend
internal/multihash: add a test
internal/blobstore: more understandable comment
add blobstore dependency
internal/router: add support for id resolving

We allow non-specific ids in API paths.
The details of the id resolution are kept
out of the router - that responsibility is
up to the API version implemention,
and will be implemented in a subsequent branch.
internal/router: add test
add new dependencies
Merge pull request #25 from rogpeppe/008-blobstore

internal/blobstore: new package

This implements the API that we need for storing
blobs, layered onto juju/blobstore.
Merge pull request #27 from rogpeppe/011-resolve-id

internal/router: add support for id resolving

We allow non-specific ids in API paths.
The details of the id resolution are kept
out of the router - that responsibility is
up to the API version implemention,
and will be implemented in a subsequent branch.
Implement the store.AddBundle method.
Also implement a cstomized CharmURL type so that
we can easily deal with partial URLS.