CI update, badge update, and travis cleanup

[dylan-asmar]

• Updated CI to include ubuntu, windows, and macOS
• Updated README badges
• Added support fo Finite HorizonPOMDPs v0.3
• Added .vscode to .gitignore
• Cleaned up remnants of Travis-CI

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (a5e26fd) 96.03% compared to head (484d654) 96.33%. Report is 9 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #16 +/- ## ========================================== + Coverage 96.03% 96.33% +0.29% ========================================== Files 2 2 Lines 101 109 +8 ========================================== + Hits 97 105 +8 Misses 4 4 ```

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