Local url validation and forms auth fix to fix #893

Added a new extension method on context to validate whether a url
path is local to the current request.

Plumbed in the new method to forms auth so it only redirects to
to a querystring url if it's local.
Merge pull request #895 from grumpydev/OpenRedirect-893

Local url validation and forms auth fix to fix #893
Added Html helpers for CurrentUser for use in Razor views
Made CurrentUser return IUserIdentity instead of Username
Remove redundant package references from Nancy.Testing
Remove unused references from Nancy.Testing
Updated and added PathCulture convention

The convention will now strip the culture from the URL, if it
was a valid culture, before passing it along for route matching
Merge pull request #897 from damianh/NancyTestingRefs

Clean up Nancy.Testing package and project references
Merge pull request #896 from jchannon/CurrentUserViewItem

Added Html helpers for CurrentUser for use in Razor views
Updated version number
Added configuration object to fix #832 and fix #902

Configuration object allows enabling/disabling the localhost
rewrite and also to specify a callback for unhandled
exceptions
Merge pull request #903 from grumpydev/SelfhostUpdates

Added configuration object to fix #832 and fix #902
Merge pull request #898 from thecodejunkie/pathcultureurlrewriting

Updated and added PathCulture convention
Attempt to fix the CI build
Fixed #908

Accept header now always set if we go through negotiation. Initially
considered only setting it if the negotiator could match more than
one type (either by having a wildcard or multiple entries), but there's
still a chance that a processor may match in some weird and wonderful
way behind the scenes so seems sensible to always add it if we have
negotiated the response.
Merge pull request #910 from grumpydev/AcceptHeaderFix

Fixed #908
Fix for #911
Merge pull request #912 from grumpydev/BlankPathFix

Fix for #911
Updated CsQuery
Fixed casing in nuspec file