Handle deprecated Matroska Elements

[FreezyLemon]

Closes #117.

There was a bug in skip_master (now skip_element) where it didn't skip all of the Element data which was easy to fix.

Also removed some serialization functions that aren't used anymore.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 50.00000% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 48.49%. Comparing base (8944849) to head (703875e).
⚠️ Report is 9 commits behind head on master.

Files with missing lines	Patch %	Lines
src/serializer/elements.rs	0.00%	6 Missing ⚠️
src/permutation.rs	80.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #133      +/-   ##
==========================================
+ Coverage   46.84%   48.49%   +1.64%     
==========================================
  Files          14       14              
  Lines        2741     2584     -157     
==========================================
- Hits         1284     1253      -31     
+ Misses       1457     1331     -126     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[Luni-4]

Thanks a lot! This is really fantastic!

Just a simple nit