Change API to better align to current TypeScript norms

[kitsonk]

The configuration of dts-generator does not easily align well to make it easy for someone who is currently using the TypeScript ecosystem with a tsconfig.json file.

We should consider breaking the API and providing a cleaner, more concise version of dts-generator that fits better into current TypeScript configurations.

[taoqf]

it will be nice use require instead of fs, i find require can read tsconfig.json in hanson style