Refactored get methodology in CmixAPIClient for use by CMixProject fu…

…nctions

Refactored delete method in CmixAPIClient for use by CMixProject functions

Added functions to CmixAPIClient:
get_projects()
get_survey_data_layouts(survey_id)
get_survey_locales(survey_id)
get_survey_sections(survey_id)
get_survey_simulations(survey_id)
get_survey_termination_codes(survey_id)
get_survey_sources(survey_id)

Created a CMixProject class and added functions:
CmixProject.delete_group(group_id)
CmixProject.delete_project()
CmixProject.get_full_links()
CmixProject.get_groups()
CmixProject.get_links()
CmixProject.get_locales()
CmixProject.get_markup_files()
CmixProject.get_project()
CmixProject.get_respondent_links()
CmixProject.get_sources()
CmixProject.get_surveys()

Added test URLs

Rename src directory to facilitate library usage

Improve documentation

Initial release with minimal functionality used by PopResearch