Added some notes about json file and alternative for ubuntu installation

README.md

@@ -16,6 +16,11 @@ Run `get_image` on the provided `simple.frag` shader to test that it works. E.g.
 ./get_image --persist simple.frag
 ```
 
+#Note:
+
+You should also have a file with the same name as the shader but with a .json extension.
+This file should only contain an "{}"
+
 ## Usage
 
 `./get_image <PATH_TO_FRAGMENT_SHADER>`
@@ -46,6 +51,12 @@ On Linux or OSX:
 bash buildscripts/1-install-deps-travis.sh
 ```
 
+Alternativly on Ubuntu you can:
+```bash
+sudo apt-get install libgles2-mesa-dev
+```
+
+
 (This will probably fail with an error at the last step, but all that matters is that the deps are created)
 
 Once you have the deps downloaded, you can build with CMake as follows:
@@ -77,4 +88,4 @@ but are not entirely sure.
 
 Note that you will see an awful lot of warnings. This is fine. As long as the build exits successfully,
 try running the generated executable (in either Debug or Release in your build directory) on sample.frag
-in the root of this project. If you get a pretty image called output.png then it has worked.
+in the root of this project. If you get a pretty image called output.png then it has worked.