add version.py and badges in README

+ add version.py for a explicit list of release history
+ setup.py: grab version number from version.py, instead of manual change
+ README: add badges, to be consistent with other insarlab repos

README.md

@@ -1,3 +1,9 @@
+[![Language](https://img.shields.io/badge/python-3.6%2B-blue.svg)](https://www.python.org/)
+[![CircleCI](https://img.shields.io/circleci/build/github/insarlab/PyAPS.svg?logo=circleci&label=test)](https://circleci.com/gh/insarlab/PyAPS)
+[![Version](https://img.shields.io/badge/version-v0.3.1-green.svg)](https://github.com/insarlab/PyAPS/releases)
+[![License](https://img.shields.io/badge/license-GPLv3-yellow.svg)](https://github.com/insarlab/PyAPS/blob/main/LICENSE)
+[![Citation](https://img.shields.io/badge/doi-10.1029%2F2011GL048757-blue)](https://doi.org/10.1029/2011GL048757)
+
 ## PyAPS - Python based Atmospheric Phase Screen estimation
 
 This python 3 module estimates differential phase delay maps due to the stratified atmosphere for correcting radar interferograms. It is rewritten in Python 3 language from PYAPS source code and adapted for ECMWF's ERA-5 corrections. 

setup.py

@@ -4,14 +4,21 @@
 from setuptools import setup, find_packages
 
 
+# Grab from version.py file: version
+with open("src/pyaps3/version.py", "r") as f:
+    lines = f.readlines()
+    line = [line for line in lines if line.strip().startswith("Tag(")][0].strip()
+    version = line.replace("'",'"').split('"')[1]
+
+
 # Grab from README file: long_description
 with open("README.md", "r") as f:
     long_description = f.read()
 
 
 setup(
     name='pyaps3',
-    version='0.3.0',
+    version=version,
     description="Python based Atmospheric Phase Screen Estimation",
     long_description=long_description,
     long_description_content_type="text/markdown",

src/pyaps3/version.py

@@ -0,0 +1,20 @@
+#!/usr/bin/env python3
+# Author: Zhang Yunjun, Nov 2021
+# Copyright 2012, by the California Institute of Technology.
+
+
+import collections
+
+# release history
+Tag = collections.namedtuple('Tag', 'version date')
+release_history = (
+    Tag('0.3.1', '2021-11-26'),
+    Tag('0.3.0', '2021-11-15'),
+    Tag('0.2.0', '2021-08-31'),
+    Tag('0.1.0', '2019-04-07'),
+)
+
+# latest release
+release_version = 'v{}'.format(release_history[0].version)
+release_date = release_history[0].date
+