update Python version to 3.6

Author: Matthew Garthwaite

.travis.yml

@@ -1,6 +1,6 @@
 language: python
 python:
-  - "3.4"
+  - "3.6"
 install:
   - sudo apt-get update
   - wget https://repo.continuum.io/miniconda/Miniconda3-latest-Linux-x86_64.sh -O miniconda.sh;

README.md

@@ -7,9 +7,10 @@ CoRAL is a library of tools for analysing the response of corner reflectors (or
 
 ### Dependencies
 
-This package requires the following non-standard Python modules installed:
+This package requires the following:
 
 ```
+Python==3.6
 NumPy
 Matplotlib
 Rasterio