There are plenty of tests for the basic behaviour of the extension
detector and how IE favours the extension from the first question mark
segment that has a dot in the next segment.
But it was missing a test for the main use case the library exists
for, which is extensions in query strings when there is a file name
with extension already (but the dot is urlencoded).
Change-Id: I0f2e1387ae42da68020f1d793bb9eb5a87a06f24
