docs: Add output of recast --help to README (#89)

* Clarify installation with pip
* Add output of recast --help to README
* Link to ATLAS Exotics Workshop 2018
   - c.f. https://indico.cern.ch/event/710748/contributions/2982534/subcontributions/254796

README.md

@@ -10,28 +10,59 @@ ATLAS tools to facilitate integration of ATLAS analyses into RECAST
 
 ### Install
 
-This package is installable via the standard Python package management tools. E.g.:
+`recast-atlas` is installable from PyPI using `pip` inside of your Python virtual environment
 
 ```
 python -m pip install recast-atlas
 ```
 
+### CLI API
+
+The `recast-atlas` CLI API:
+
+```
+$ recast --help
+Usage: recast [OPTIONS] COMMAND [ARGS]...
+
+Options:
+  -l, --loglevel TEXT
+  --help               Show this message and exit.
+
+Commands:
+  auth       Authentication Commands (to gain access to internal data)
+  backends   The RECAST computational backends.
+  catalogue  The RECAST Analysis Catalogue
+  ci         Helper Commands for CI systems
+  retrieve   Retrieve RECAST Results from asynchronous submissions
+  run        Run a RECAST Workflow synchronously
+  software   Build Container Images for RECAST
+  status     Get the Status of a asynchronous submission
+  submit     Submit a RECAST Workflow asynchronously
+  tests      Run a test
+```
+
 ### Running RECAST
 
-The `recast` tool aims to enable both local execution as well as asynchronous execution on a [REANA](http://reana.io) cluster. Via the
+`recast-atlas` aims to enable both local execution as well as asynchronous execution on a [REANA](http://reana.io) cluster.
+
+#### Local backend
 
-#### Locally:
+Running the example from the [ATLAS Exotics Rome Workshop 2018][ATLAS Exotics Workshop 2018] using the `local` backend:
 
 ```
 recast run examples/rome --backend local
 ```
 
-#### ...and on REANA
+#### REANA cluster backend
+
+Running the example from the [ATLAS Exotics Rome Workshop 2018][ATLAS Exotics Workshop 2018] using the `reana` backend:
 
 ```
 recast run examples/rome --backend reana
 ```
 
+[ATLAS Exotics Workshop 2018]: https://indico.cern.ch/event/710748/contributions/2982534/subcontributions/254796
+
 #### On [LXPLUS8](https://clouddocs.web.cern.ch/clients/lxplus.html)
 
 ```console