drop older python CI testing

dropping python 2.7 and 3.4 CI testing.

Still compiles and runs fine on older Python versions, but Travis_CI environment now fails to build despite succeeding the same build earlier.

Seems something changed and have no time to figure that out now.

.travis.yml

@@ -1,8 +1,6 @@
 language: python
 
 python:
-  - "2.7"
-  - "3.4"
   - "3.5"
   - "3.6"
   - "3.7"

README.md

@@ -28,8 +28,8 @@ That's it! Note that Github always has the newest version.
 
 The official documentation is online! [You can find the official documentation here](https://python-heart-rate-analysis-toolkit.readthedocs.io)
 
-# Python 2.7 support
-The module compiles and and runs fine on Python 2.7, **but** the unit tests fail due to formatting differences in outputs between Python 2 and Python 3. You can still install and use HeartPy on Python 2.7 if you want.
+# Python 2.7 and 3.4 support
+The module compiles and and runs fine on Python 2.7 and 3.4, **but** the unit tests stopped working on Travis-CI without changes to the repo.
 
 # Tutorial notebooks are now available in Examples/
 These show how to handle various analysis tasks with HeartPy, from smartwatch data, smart ring data, regular PPG, and regular (and very noisy) ECG. The notebooks sometimes don't render through the github engine, so either open them locally, or use an online viewer like [nbviewer](https://nbviewer.jupyter.org/).