Issue #359 ASP.NET Ajax requests not displayed

ASP.NET Ajax requests have a content type of "text/plain" and so were
filtered out by Glimpse
Updated comment to match fix for Issue #359
Updated class level comment and fixed Unit Test
Tweaked comments
Merge remote-tracking branch 'upstream/master'
Merge pull request #425 from grahammendick/master

ASP.NET Ajax requests not displayed (Issue #359)