Show minimal page if there are no logged requests

This fixes #171
Fix potential CSS style clashes.

Separated the toolbar.css file so no class styles are injected when rendering non debugtoolbar pages.
stop printing toolbar handle icon; uniform spacing
Merge pull request #175 from tisdall/master

stop printing toolbar handle icon; uniform spacing
Add changelog entry
fix to handle XHTML
replace entity not available for XHTML
Merge pull request #176 from parly/master

Fix to handle XHTML
Merge pull request #171 from wichert/first-request

/_debugtoolbar/ is a 404 until request hit the main app
update changelog
Merge branch 'fix_css_clash' of tr11/pyramid_debugtoolbar into pull.174
Merge branch 'pull.174'
update changelog
prep 2.2