workaround firefox different handling of hash decoding for unicode tags

The problem is explained there :
http://stackoverflow.com/questions/1703552/encoding-of-window-location-hash

As a summary, the hash exposed in JS in Firefox is already URL-encoded, which
is not the case in Chrome for instance.

public/js/selfoss-events.js

@@ -81,7 +81,7 @@ selfoss.events = {
             selfoss.filter.tag = '';
             selfoss.filter.source = '';
             if( selfoss.events.subsection.substr(0, 4) == 'tag-') {
-                selfoss.filter.tag = selfoss.events.subsection.substr(4);
+                selfoss.filter.tag = decodeURIComponent(selfoss.events.subsection.substr(4));
             } else if( selfoss.events.subsection.substr(0, 7) == 'source-') {
                 var sourceId = parseInt(selfoss.events.subsection.substr(7));
                 if( sourceId ) {