Implement disk based FileSystem and Provider

Ent provides a small HTTP interface to manage blobs namespace
partitioned by buckets. Depending on the FileSystem implementation used
it needs to run as a single instance per host or as many instnaces
scaled out horizontally.

Within a bucket, you can use any name for your objects, but bucket
names must be unique. Only one Owner can exist per Bucket.
Merge pull request #1 from soundcloud/first-iteration

Implement disk based FileSystem and Provider