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
Invoicing support
Correct path for invoicing
update tests with correct endpoint
Merge branch 'invoicing'

Add invoicing rest api features to sdk
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
Merge pull request #46 from paypal/stable

Stable