Small code cleanup (#83)

## Summary

* Fix cppcheck low violations
* Remove teardown method on parsers, use destructor
* Code cleanup

lib/Epub/Epub/parsers/TocNcxParser.h

@@ -28,9 +28,9 @@ class TocNcxParser final : public Print {
 
   explicit TocNcxParser(const std::string& baseContentPath, const size_t xmlSize)
       : baseContentPath(baseContentPath), remainingSize(xmlSize) {}
+  ~TocNcxParser() override;
 
   bool setup();
-  bool teardown();
 
   size_t write(uint8_t) override;
   size_t write(const uint8_t* buffer, size_t size) override;