fixed merge to develop branch
support for nested dropzones
docs($api/methods): Remove extra deleteFile

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chore(*): Start 4.2 release cycle

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test($validation): #1063 file-based validation tests (also see #1059)
test($cancel): #1063 cancel method tests
test($file-uploads): #1063 file-based unit test refactoring
test($file-upload): #1063 start of upload unit tests

- 1st test: very simple upload
- Extended assert framework to allow for assertion counting
- Added sinon.js support for mocking XHR
- Code to mock FormData (for examining request params in tests)
- Adjustment to sinon to deal with lack of ProgressEvent constructor in phantomjs
fix($request-options): #1065 use custom request param name values
test(simple-file-uploads.js): fixes #1065 test fix
chore(karma-runner.js): squelch beforeunload handler to prevent test stall in a browser
Fix broken link to mozilla

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test(unit/simple-file-uploads.js): #1063 non-MPE upload requests
test(unit/simple-file-uploads.js): #1063 refactor to eliminate some code dupes
test(unit/file-upload-params.js): #1063 parameter-passing tests
test(unit/delete-file.js): #1063 delete file tests
test(unit/chunked-uploads.js): #1063 chunked upload tests
fix($docs): retry.autoAttemptDelay misdocumented as retry.autoAttemptsDelay

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fix(docs/features/chunking.jmd): bad logic in documentation for determining when last chunk has been recevied

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fix(docs/features/chunking.jmd): remove incoherent sentence

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