versioning
Cut a release.
Closes GH-94.
(not ready yet) initial work on HAR support. See GH-60, GH-81.
HAR improvements:

* unique request ids (not based on URLs, not based on Python object ids!);
* correct request order;
* cleaner proxy management;
* information about requests is populated as soon as possible
getarg_bool utility
'history' argument for render.json. Fixes GH-60. See GH-81.
DOCs for 'history' argument