#20 and some more

Hi @RaymondMcT ,

In reference to https://github.com/quandl/R-package/issues/20 I have tried to move from RSJSONIO to jsonlite (https://github.com/jeroenooms/jsonlite)

**Changes besides that**

- [] Improve tests for search
- [x] Add GitIgnore and R-package.Rproj file to repository
- [x] Update Changelog, Description and Namespace
- [x] New dependency: ~~roxygen2~~ for easier running of tests and builds from RStudio.
- [] Some formatting, too. BTW: What do you prefer ? I kind of used the default one from RStudio (2 tabs)-but not everywhere....