`falconparser` uses `falcon.util.uri.parse_query_string`, but uses
an incorrect keyword argument name, `keep_blank_qs_values`. the correct
argument name is `keep_blank`

see: marshmallow-code#448

this commit mostly consists of stylistic changes, for example
using `distutils.version.LooseVersion` instead of the raw Falcon
version string.

other than that, the major change is dealing all Falcon versions
greater than 1.X as using the updated keyword arg, and Falcon 1.x
versions as using the legacy keyword arg (as opposed to just
Falcon 1.x and 2.x).