Itolapi

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- Vastly simplified upload API (cli usage remains the same).
- Removed `Itol.add_variable()` function, added `Itol.params` and and `Itol.add_file`
- Lowercased all files, import from python package instead (i.e. `from itolapi import Itol`)

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- Cleanup itolapi example scripts
- Add integration tests against itol api
- Better test coverage

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- Simplify tests and get to 100% test coverage
- Several code refactors

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- Switched to itol4
- Removed itol2 support

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- Many internal changes to update packaging and testing

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- Basic support for itol2
- README fixes
- Dependency updates
- Testing updates