Merge pull request #386 from bjz/comment

Add comment about submodules in README

Author: brendanzab

README.md

@@ -38,3 +38,14 @@ The Khronos XML API Registry, exposed as byte string constants.
 [build-dependencies]
 khronos_api = "1.0.0"
 ```
+
+## Compiling from source
+
+`khronos_api` uses a git submodule. You will need to initialize it before building:
+
+```sh
+git submodule update --init
+```
+
+A batch cargo script is provided at `bin/cargo`. [See the script](https://github.com/bjz/gl-rs/blob/master/bin/cargo)
+for some example usages.