Merge pull request #18 from nonbeing/master

Added --skip_ssl_cert_check option
For http status 503, do a retry
Merge pull request #19 from Randgalt/master

For http status 503, do a retry
Created a DbexportCommand that wraps a call to the DbExportCommand REST API, All validations are done per
http://old.qubole.com/submit-db-export-command
Added support for modes. Added more arg validations
Merge pull request #20 from Randgalt/master

Created a DbexportCommand that wraps a call to the DbExportCommand REST API
Release 1.0.9_beta
Adding support for Presto commands to qds sdk