unified change api for both modes

[shaunlebron]

We can describe all text changes with this model: https://github.com/shaunlebron/parinfer/blob/master/test-cases/text-change.md

but right now, the parinfer api requires us to specify changes differently depending on the mode:

• indent mode - line numbers to replace, new lines to insert
• paren mode - specify a cursor-dx position indicating how far the cursor has moved

this requires a lot of manual work on the api user, so if we simply accept a change object described by the above link (which I think most editors expose on change events), we can offload this work to the modes themselves.

This should be done before #24 (creating the standalone parinfer-lib)

[shaunlebron]

since we're opting out of aggregating edits between debounces (see #75), we do not need this anymore