docs: update readme with more details

CHANGELOG.md

@@ -1,5 +1,24 @@
 # Changelog
 
+## v0.3.0 (2021-10-01)
+
+#### New Features
+
+* add option to get host names from an external file
+#### Refactorings
+
+* clean-up for pylint
+#### Docs
+
+* update docs with a _little_ more detail
+#### Others
+
+* fix spelling
+* refactor test code for pep8
+* update tests to handle all branches
+
+Full set of changes: [`v0.2.0...v0.3.0`](https://git.admin.franklin.edu/tins/checkcert/compare/v0.2.0...v0.3.0)
+
 ## v0.2.0 (2021-09-30)
 
 #### New Features

README.md

@@ -3,7 +3,7 @@
 This utility was based off of [this
 gist](https://gist.github.com/gdamjan/55a8b9eec6cf7b771f92021d93b87b2c).
 
-I have wrapped the logic in a click-based CLI and added command-line options
+checkcert has the logic of that gist wrapped in a click-based CLI and added command-line options
 (checkcert --help to see them)
 
 # Installation
@@ -11,3 +11,38 @@ I have wrapped the logic in a click-based CLI and added command-line options
 ## from PyPi
 pip install checkert
 
+# Usage
+
+When you run `pip install checkcert`, you will get a `checkcert` command.  To
+show all the options, simply run `checkcert --help` to get the most-current list
+of commands and options.
+
+### Basic Usage
+The basic usage is `checkcert example.com`
+
+### Check cert with an alternate port
+
+Anywhere you specify the host, you may use the format `host:port` to specify an
+alternate port.  If no port is specified, 443 will be used.  To check something
+running on port 8081 for example, execute `checkcert example.com:8081`
+
+### Multiple domains
+
+checkcert will take all domains specified on the command line.  Multiple values
+may be specified as `checkcert example.com www.example.com alt.example.com:444`
+
+### Domain list from a file
+
+checkcert can be instructed to pull the list of domains from a file instead with
+the --filename option.  The file contents will just be a domain per line
+(specified in host:port format, or just host to default to port 443)
+
+create a file named domains.txt with contents like the following
+
+```
+example.com
+www.example.com
+alt.example.com:444
+```
+
+Then execute `checkcert --filename domains.txt`