added tests proj and clock abstraction to existing implementation
abstracted backing cache implementation for testing purposes
cache expiry now based on lesser of token expiry or cache settings
remove introduced dependency on thinktecture.identitymodel
tidied up test to make it clearer
Merge pull request #14 from thirkcircus/cache-honor-tokenexpiry

Honor token expiry when setting cache expiry
cleanup after PR
updated nuspec
updated build script for appveyor
Merge branch 'master' into dev
updated build script