Fixed misdescriptions on README.rst

The readme had two misdescriptions:

- In server:main section of app.ini, used makky as a server

  - Fixed to use gunicorn#main (gearbox#wsgi is good too).

- 'gearbox serve' expects the .ini file from -c option
Merge pull request #1 from hirokiky/patch-1

Fixed misdescriptions on README.rst