Tidy code. Switch to jsonlite. Remove implicit plyr dependency. Fix some bugs (getSegments).

Changes:

- tidy source code: fromtatR:tidy.source + manual fixing;
- switch to use `jsonlite::fromJSON`;
- fix bugs: `getSegments` function contain incorrect names for extracting, `getMCFData` contain calls `plyr::llply` functions.
- some litle improves.