Simplify API

[nchen63]

• Remove tslint.ts and interfaces associated with single file Linter
• Rename tslintMulti.ts -> linter.ts
• Rename lint.ts -> index.ts
• Remove old ILinterOptions and rename IMultiLinterOptions ILinterOptions
• Reference index.js/index.d.ts in package.json

Upgrade Instructions for 3rd party apps using the API

• move the configuration property off of ILinterOptions and pass it into lint()
• move filename and source from the constructor to lint()
• you have to call Linter::getResult() to get the result instead of being returned from `lint()

fixes #1595

[adidahiya]

this looks good, but I forgot about @jkillian's comment here: #1595 (comment)

how much effort will be required for third-party tools to transition to using the new Linter class?

[nchen63]

It's pretty straightforward to migrate to the new Linter class. You can see the changes that I made to the test.ts class here: https://github.com/palantir/tslint/pull/1720/files#diff-c1e1ffc130aead13aa199b62448b178c

• move the configuration property off of ILinterOptions and pass it into lint()
• move filename and source from the constructor to lint()
• you have to call Linter::getResult() to get the result instead of being returned from lint()

[nchen63]

I also made the new linter throw an error if configuration was included on the ILinterOptions object since not moving it would still work but use the default config

[panuhorsmalahti]

I noticed that 'findConfiguration' API seems to have been changed a bit (or maybe the function which uses it's result). Anyway, I had to change my code to use the .results property of the return value of findConfiguration. Maybe this will help someone.