Add customizable API request

Maybe developers want request the API via CLI tool and get a JSON response:

```
$ twe get users/show --id=litomore

$ twe get statuses/home_timeline --count=20 --include-rts=false

$ twe post statuses/update --status=hi
```

Even they can debug the response in REPL:

```
$ twe get users/show --id=litomore --repl
```