Don't count non-standard answer when calculating wait time mode
added tests for analyze and get_mode
some tests for survey utils
merged develop into this
improved tests coverage of surve/utils.py
fix bug in core/utils/extract_attr and improve test coverage overall
removed comments
improved test coverage
fixed flake8 issues
Merge branch 'develop' into 181-non-standard-answers
fixed calculation of patient satisfaction in RegionReportView
Merge branch '181-non-standard-answers' into patient-satisfaction

Merge the two to deploy to staging
fixed merge issues
Merge pull request #183 from caktus/181-non-standard-answers

refs #181 - Don't count non-standard answer when calculating wait time mode