Add a citation snippet

[kingroryg]

Is there a defined way to cite tiny-dnn. If yes, we should add it to the main README.

Something like,

@Manual{,
    author = {Names of authors},
    title = {tiny-dnn: header only, dependency-free deep learning framework in C++14},
    year = {2017},
    url = {http://tiny-dnn.readthedocs.io},
  }

[febinpsunny]

Hey have you guys decided on something like this ? I have used your framework in my research and would like to cite you guys !!