Add installation guide in README

[cadeath]

Sorry for this post, but I am having problem on running this git.
Or maybe I don't know how...

Can you please provide a quick guide? thanks

[eubnara]

I think the problem is caused by gradle / react-native-vector-icons version conflicts.
NativeBase-VectorIconApp uses gradle 2.2.3 ver. (https://github.com/GeekyAnts/NativeBase-VectorIconApp/blob/master/android/build.gradle#L8)
Gradle 2.2.3 cannot recognize google() directive in build.gradle. However, react-native-vector-icons >= 6.1.0 uses this directive.
If someone wants to fix this problem, there are two solutions.

1. Upgrade gradle version of this project.
2. Just use react-native-vector-icons@4.6.0
   • At project's home
   1. npm install react-native-vector-icons@4.6.0
   2. npm install
   3. npm run start or react-native start
   4. npm run android(react-native run-android) or npm run ios (react-native run-ios)
      • refer to package.json

I think 447174a#diff-8ee2343978836a779dc9f8d6b794c3b2 causes this issue.