Tweak docs before releasing 0.19

Reviewed By: mkonicek

Differential Revision:D2883844
Ninja: Only docs and React Native website, doesn't affect any fb apps

fb-gh-sync-id: 4bf56dc695224f172832ca5381cebceab9e5fe4f

[0.19.0-rc] Bump version numbers

Revert "Dont call npm before node is available"

This reverts commit 7ecb693.

This breaks Xcode build, see discussion on facebook#5156

[0.18.0-rc] Bump version numbers

[0.17.0] Bump version numbers

Make the NetInfoModule not crash when permission is missing

Depend on 0.16.1 binaries from custom JCenter repo

Only needed until the artifacts propagate to Maven Central.

[0.16.0-rc] Bump version numbers

[0.15.0] Bump Maven version number

[0.14.2] Include nvm fix in react-native-xcode.sh