Feature/support 0.40

[mlabrum]

Hey,

I've made the changes that RN 0.40 requires, and I've also upgraded the example project to 0.40

Thanks

[gcarling]

@naoufal Can you please merge this? We rely on this in our project and would really love to be able to keep using it past RN-0.40. Thank you!

[ThisIsMissEm]

Can I point you to: https://medium.com/@thisismissem/how-to-upgrade-react-native-modules-in-a-backwards-compatible-manner-a5b5c48d590c

It's a way to do this in a backwards compatible manner.

[g3r4n]

I've make it backwards compatible in #27

[g3r4n]

Please merge this one because It's preferable to not backwards compatible module, in order to always support the last version of RN. previous version will support RN<0.40

[g3r4n]

@mlabrum can you update the Readme with the version that support RN <0.40.0 and update the package.json ?

[u0x01]

pleaseeeee merge this pr, we need it! @naoufal

[naoufal]

@u0x01 @g3r4n @ThisIsMissEm @gcarling @mlabrum merged and published to npm under 3.0.0.