updated bonnie to use the updated bundler that handles simplexml
tied in new structure for stratifications
Merge pull request #295 from projecttacoma/simple_xml_parser

Integrate Simple xml and HQMF R2 parsers
Initial date_shift rake task for shifting source_data_criteria ranges by specified intervals
Update description and resolve issue with undefined end dates
Clean up multiple environment arguments for rake task
Utilize bonnie.yml 'measure_period_start' to specify MP
Reduce effective_date computation arithmetic operations
Include patient birthdate and deathdate in date shift task
Also shift timestamp field values on patient data criteria
Use Time.advance for precision date shifting instead of Rails Time arithmetic operators