fontique: Clear weight, style and stretch when parsing the fontconfig…

… cache (#104)

The fonts do not always have these pattern elements defined, and then
the value of the previous font was wrongly used. Clearing the values,
fixes that and ensures that the default values are used. For a more
detailed description see
#92 (comment)

* Fixes #93 
* Fixes #95
* Fixes #96

fontique/src/backend/fontconfig/cache.rs

@@ -79,6 +79,9 @@ impl CachedFont {
         self.path.clear();
         self.index = 0;
         self.coverage.clear();
+        self.weight = Weight::default();
+        self.style = Style::default();
+        self.stretch = Stretch::default();
     }
 }