Fix README Go version requirements

MobileLibrary/Android/README.md

@@ -37,7 +37,7 @@ When that command completes, the compiled `.aar` files (suitable for use in an A
 ##### Prerequisites:
 
  - The `build-essential` package (on Debian based systems - or its equivalent for your platform)
- - Go 1.9 or later
+ - Go 1.13 or later
  - Full JDK
  - Android NDK
  - Android SDK

Server/README.md

@@ -7,7 +7,7 @@ Functionality is based on the [legacy server stack](https://bitbucket.org/psipho
 
 ### Build
 Prerequisites:
- - Go 1.9 or later
+ - Go 1.13 or later
 
 Build Steps:
  - Get dependencies: `go get -d -v ./...`