interface{} -> any

[garyburd]

Replace uses of interface{} in the code with the alias any.

Steps:

1. Run gofmt -w -s . at the root of the project.
2. Hand edit comments and string literals to replace interface{} with any. The templates in nvim/api_tool.go are a notable example of where hand editing is required.
3. Run go generate.

This change can create merge conflicts for work in progress. Should this change wait on any work in progress?

[justinmk]

Should this change wait on any work in progress?

The only non-trivial open PR is #95 and it doesn't look like it will be hard to adapt to this change. @zchee

[zchee]

@garyburd go ahead to will conflicts change. I can following your (repository) upstream change anytime