Version 0.9.15

Contributing Guidelines #1236
Wrap for attribute in quotes #963b051ecb
Ensure choice count is reflective of actual selected item count. #1171
Delete choice refactor #1232
Fix scroll issue in Prototype version #1213
Use the better supported offsetWidth property to get a fields width #1172
Merge branch 'master' of https://github.com/harvesthq/chosen into fixed_onkeypress_event