Merge branch 'hotfix/4.1.1'
chore($hotfix) prepare for 4.1.1 release
docs(api/options): Fix incorrect option types

fixes #1082 for the `multiple` and `acceptFiles` options.

[skip ci]
docs($acceptFiles option): Fix option parameter type

Using an array of strings as the value of the `acceptFiles` options does not
appear to conform to HTML spec, and is not guaranteed to work on all browser
implementing the spec. Using a comma-separated list of mimetypes is a better
option.

Fixes #1082

[skip ci]
docs($customHeaders options): Clarify scope on request, and add a couple missing entries
Merge pull request #1086 from paulmelnikow/doc_custom_headers

docs($customHeaders options): Clarify scope of request.customHeaders, and add a couple missing entries
docs(*): merge in master to grab doc fixes

[skip ci]