update Dockerfile to follow conventions

change instructions to be uppercase
change ADD to COPY
change cmd exec docker-registry to CMD ["docker-registry"]
Merge pull request #620 from unclejack/dockerfile_changes

update Dockerfile to follow conventions
fix forgotten lowercase cmd
Merge pull request #621 from unclejack/uppercase_cmd

fix forgotten lowercase cmd
Config template: add boto_calling_format S3 option

Using the "ordinary" calling format can be useful when using
a bucket whose name contains periods (otherwise the AWS SSL
certificate may be refused because it is several subdomains
deep).
Merge pull request #625 from krallin/aws-calling-format

Config template: add boto_calling_format S3 option
Correcting typos in the {ADVANCED, CONTRIBUTING, README}.md files.
Merge pull request #628 from krook/fix-markdown-typoes

Correcting typos in the {ADVANCED, CONTRIBUTING, README}.md files.
Do not use conflicting module names for bugsnag
Do not use conflicting module names for newrelic
Alphabetical ordering of imports
Merge pull request #638 from gregburek/bugsnag

Do not use conflicting module names for bugsnag or newrelic
Use gevent to parallelize storage operations in get_tags

This is a band-aid for #614

For context, hosted from a GCE instance with GCS being the backing
store, With this patch, we are able to 'docker pull' 859 tags without a
timeout.  Prior to this patch, we were *unable* to pull anything from a
repository with 200 tags.  This is the extent of my investigation thus
far.  Unfortunately, this change is probably just a constant factor
reduction in run-time as total network round-trips still grows linearly
with tag count.
README.md: Shift Index discussion to the external-backend section

We use Index for third-party search engines.  For the 'sqlalchemy'
special case, we use SQLAlchemyIndex.
README.md: Document --preload for the SQLAlchemy search index
avoid using same variable twice in the same function
Merge pull request #659 from misho-kr/master

avoid using a variable twice in the same function
Merge pull request #655 from wking/document-preload

README.md: Document --preload for the SQLAlchemy search index
docker-registry-driver-azure config and docs

Signed-off-by: Ahmet Alp Balkan <ahmetalpbalkan@gmail.com>
Merge pull request #664 from ahmetalpbalkan/master

Azure Storage Driver config and README updates