add xvfbwrapper to requirements.txt
add xvfbwrapper to setup.py
bump version to 1.1; add a changelog for this release
cleanup: simplify parameter handling code by using keyword arguments
cleanup: use dicts more consistently
cleanups
cleanup for doRequest methods of WebpageRender subclasses
fail earlier in case of exceptions in doRequest
rename doRequest to start
allow to pass headers to WebpageRender explicitly
allow to pass http method and request body to WebpageRender
fixed "wait" in UI
track more classes in /debug
more proxy vs proxy server renames
proxy factories refactor: they no longer read directly from request
handle validation errors in pool._start_render