Handle non-ascii characters in platform version shown in Versions panel.

Non-ascii characters in platform name, for example Fedora's <<Schrödinger’s Cat>>
causes VersionDebugPanel to fail with UnicodeDecodeError. Added compat.text_(.., 'utf8')
convertion and moved platform name discovery to helper method to be easily swaped in unit tests.
Docs - fix 1.0.5 is current release
Merge pull request #104 from brodul/documentation_fix

Docs fix - 1.0.5 has been released
Merge branch 'master' of github.com:hanula/pyramid_debugtoolbar into hanula-master
add changelog entry
.decode('utf-8') added on text lines returned to templates
PEP8 fix
call text_ instead of decode
Test for passing utf-8 encoded exception message to template.
Decode string in escape utf-8 if not ascii decodable.
Merge pull request #108 from brodul/text_to_templates

Better unicode support when passing values to templates.
Note about Firefox versions and Selenium compatability.
Fix missing semicolons.
Merge pull request #114 from brodul/js_minor_fixes

Fix missing semicolon in toolbar.js
raise a URLDecodeError rather than a plain UnicodeDecodeError when the path cannot be decoded; see Pylons/pyramid#1057
Update index.rst

Make it easier for Intersphinx to point at the scrolled-down start of the doc.
Update index.rst

Dang, underscore.
render the exception a second time below traceback. especially template tracebacks are quite long sometimes, showing the exc below the traceback makes it easier to understand the context
see github issue #54. Introducing a new configuration option : debugtoolbar.show_on_exc_only = true/false. If true the debug toolbar will only be rendered if an exception occurs; if the request does not raise a exception no additional html code will be added to the response.
tests for new show_on_exc_only configuration option