Added example of advanced use and support for prop `style`

With support prop `style`, any css styles can be set for picker root
element. Added advanced example into example directory and its simplifed
version rewritten to README.
Watch with `browserify` task turned off, added yargs for gulpfile aguments

Browserify task should been run from hand with decision if development or production version (with
or without source maps) should been generated so it was commented out at watch task.
Providers `index.js` and `stylus.js` added

Added `index.js` that exports Picker and `stylus.js` that provides
function for Stylus renderer.
Fixed browserify use and setting `debug` option, added requiring React

Use of gulp-browserify is deprecated technique, so use native module, see
https://medium.com/@sogko/gulp-browserify-the-gulp-y-way-bb359b3f9623. Fixed
use of `yargs` for getting `production` option and set of `debug` browserify
flag. Added require of React into all source files to enable bundle it with
target application (instead use prebundled Picker). Added browserify-shim to
preserve generating standalone dist script without React included.
Component require example and uglifying added, moved browserify transform def

Added uglifying of dist script into `browserify` task. Added new examples of
component require into README. Definition of browserify shim transform moved
from `package.json` to task.
Bumped version to 0.2.0
v0.2.0 - improved creation of dist script, added `style` prop, extended README

- added support for prop `style` that can change root element styling
- added deciding of production and development browserify build by gulp args
- added more examples and better description into README
- style of disabled picker parts (calendar, spinners) modified to be more
  obvious their state
- added package "exporters" - files for exporting component and its style via
  standard  commonjs/stylus interface
- changed browserify task -> use of native browserify module, added uglifying
  and shiming React
- delay before permanent incrementing start halved
- added tests coverage task
Merge tag 'v0.2.0' into devel