Merge branch 'rel-1.0.0' into stable

Response tag removed, prepare for release
Merge branch 'stable' of github.com:paypal/rest-api-sdk-python into stable

Log handling and dependency of six
Merge pull request #44 from paypal/stable

Merge pull request #43 from paypal/rel-1.0.1
Support Invoice APIs
Invoicing support
Correct path for invoicing
update tests with correct endpoint
Merge branch 'invoicing'

Add invoicing rest api features to sdk
Update invoice endpoint
Added invoice samples
Update README with invoicing samples
Correct syntac for invoices_tests
Fix fonts on readme
Merge branch 'rel-1.1.0' into stable

Merge in release branch for 1.1.0