Add support for Azure AD - improvements (#34)

Use an interface for the SP provider object to avoid adding "github.com/Azure/go-autorest/autorest/adal" as a dependency to this module
Also, fixed test that was leftover from before.
Improves upon #33

Delete* methods were missing the opts parameter (#25)

Add MIT license to LICENSE file (#24)

Merge pull request #13 from jeryanders/master

Changed type for PartitionKey on RequestOptions to interface{}

Merge pull request #11 from felipecruz91/feature/query-with-partition…

…-key

Query documents using partition key.

test(documentdb): test executeSporc