List vaults, blocks, files with bad marker
Replace storage-url with service-catalog
Merge branch 'master' into service_catalog
Merge branch 'master' into negative_markers
feat: HEAD /blocks/{block_id} endpoint

on a HEAD, the block is checked for existence in the metadata store,
after which its checked for existence in block storage.

- If present in metadata, and non-existent in block storage:
     502 Bad Gateway is returned along with an explanation.

- If present both in metadata and block storage.:
     200 OK is returned along with headers such as
     x-block-reference-count

- If not present in metadata:
     404 Not Found is returned
move:consistency check logic from resource to model

Addressing review comments:
Consistency check now takes place in the model, and exception thrown
if consistency check fails. The exception is caught in on_head function
of Block's Item Resource and corresponding status code (502) set
in response.
Support Block HEAD
Merge remote-tracking branch 'upstream/master' into head_block_endpoint
fix: check for block existence instead of getting the block

the model now has a has_block() function which checks for existence
in both metadata and storage.
Merge branch 'master' into head_block
chore: remove old config.py reference

This patch removes a reference to config.py which no longer exists
check: vault existence

return a 404 if the vault does not exist.
fix: status code 200 to 204

Addressing Xuan's comments:
Since we are returning an empty body here, with most information
in the headers, we return a 204 with RESTful standards in mind.
log: default logging behavior

use the rotatelogfile handler to log to a file.
exception: Consistency Error fix

- Fix Consistency Error Exception to be very explicit about what went
  wrong. The ConsistencyError Exception now outputs a message regarding
  the blockid, vaultid and the project id that caused the exception, and
  that message is logged.

- Prefix helper functions not intended for public consumption with '_'
Merge pull request #139 from jc7998/service_catalog

Replace storage-url with service-catalog
Merge pull request #140 from jc7998/negative_markers

API Tests: List vaults, blocks, files with bad marker
unify: change format for assigning blocks

Its now of the form:

POST /v1.0/vaults/{vault_id}/files/{file_id}
body:

[
    ["fecfd28bbc9345891a66d7c1b8ff46e60192d284","0"],
    ["63cac3ed731e4b1f868cb3adaef591464de54a67","100"],
    ["a6f76d7c3b9e2576fa74c5dc438304bcdf3247d0","200"]
]
fix: app can now be started using gunicorn, uwsgi

There was an import error that needed to be fixed, in the
way the driver was imported.
Merge pull request #171 from TheSriram/fix_app

fix: app can now be started using gunicorn, uwsgi