API Change: gotStatus option: headers argument: all property values are now always arrays
readme.markdown: documenting 'headers' option and 'headers' argument for 'gotStatus' option
readme.markdown: documenting the return value
-browser: correctly handle 'headers' option
-browser: validate input headers (check for forbidden headers like Content-Length) before creating a request
-browser: get readyState from xhr, not readystatechange event
-browser: call first downloadProgressCb after statusCb
-browser: do not set Content-Length request header
-browser: call finished(abortError) before calling xhr.abort, xhr.abort synchronously fires readystatechange=DONE event
-browser: check for existence of appropriate callbacks in all event handlers
release 0.0.5