Add long_description to package for release (#37)

README.md

@@ -2,3 +2,11 @@
 
 [![Build Status](https://dev.azure.com/spacetelescope/fitsblender/_apis/build/status/spacetelescope.fitsblender?branchName=master)](https://dev.azure.com/spacetelescope/fitsblender/_build/latest?definitionId=14&branchName=master)
 [![codecov](https://codecov.io/gh/spacetelescope/fitsblender/branch/master/graph/badge.svg)](https://codecov.io/gh/spacetelescope/fitsblender)
+
+FITSBLENDER
+============
+
+This package supports the creation of a combined header for a FITS file based on the contents of the headers
+of a set of input FITS images.  A rules file defines what keywords will be present in the combined
+output header as well as how the output value will be determined from the set of values from all 
+the input image headers.  

setup.py

@@ -2,6 +2,11 @@
 
 from setuptools import find_packages
 from setuptools import setup
+from pathlib import Path
+
+
+this_directory = Path(__file__).parent
+long_description = (this_directory / "README.md").read_text()
 
 PACKAGENAME = 'fitsblender'
 
@@ -36,6 +41,8 @@
     author='Michael Droettboom',
     author_email='help@stsci.edu',
     description='Aggregate values in FITS headers',
+    long_description=long_description,
+    long_description_content_type='text/markdown',
     url='https://github.com/spacetelescope/fitsblender',
     classifiers = [
         'Intended Audience :: Science/Research',