Added development notes. Standardized blender version used for

regression tests and fixed travis build

.travis.yml

@@ -8,11 +8,12 @@ cache:
 
 before_install:
     - sudo apt-get update
-    - sudo apt-get install --no-install-recommends -y libsdl1.2debian
+    - sudo apt-get install --no-install-recommends -y libsdl1.2debian pep8 python3-pip
+    - sudo pip3 install pylint
 
 install:
     - tests/install_blender.sh
     - source .envs
 
 script:
-    - make all BLENDER=$BLENDER_BIN
+    - make all BLENDER=$BLENDER_BIN PYLINT=pylint

README.md

@@ -12,11 +12,35 @@ export process to [Godot Engine](https://godotengine.org) as straightforward as
    folders there from other addons). Copy the entire dir and not just its
    contents.
 2. Go to the Blender settings and enable the "Godot Exporter" plugin.
-3. Enjoy hassle-free export.
+3. Export your file with `File` -> `Export` -> `Godot Engine (.escn)`
 
 If you find bugs or want to suggest improvements, please open an issue on the
 upstream [GitHub repository](https://github.com/godotengine/blender-exporter).
 
+## Development Notes
+
+This repository includes a Makefile to assist with development. Running
+`make` from the project root will:
+
+1. Export all of the blend files from the `tests/scenes` directory.  
+   If you add a feature, it is suggested that you add a new blend file to 
+   the `tests/scenes` directory that uses this feature.
+2. Runs `diff` on the output files conpared to the reference exports. This acts
+   as a regression test.
+3. Tuns a style check using pep8 and pylint. Your code must pass the style 
+   checks to be elegible to merge.
+
+
+Due to differences in blender versions creating minor differences in the 
+output files (even with the same blender release number), the regression tests 
+are best run with blender 2.79 downloaded from 
+[this exact url](http://mirror.cs.umn.edu/blender.org/release/Blender2.79/), 
+which is used for the Travis builds. If you think your blender version is 
+adequate, the hash (visble in the upper right of blender's splash screen) 
+should be `5bd8ac9abfa`. The exporter itself should run on all modern versions 
+of blender, but the output may differ slightly.
+
+
 ## License
 
 This Godot exporter is distributed under the terms of the GNU General