Fixed bug in replacement of unicode escape sequences ([NSString iss_stringByReplacingUnicodeSequences]).
Added support for processing refreshable stylesheets after normal stylesheets (processRefreshableStylesheetsLast)
Added support for setting interval at which refreshable styhesheets are refreshed (stylesheetAutoRefreshInterval)
Updated error handing for loading of refreshable stylesheets.
Added support for registering custom stylesheet properties, by exposing an instance of `ISSPropertyRegistry` through the property `propertyRegistry` in `InterfaCSS`.
Preparing for version 0.9.10.