First pass at documenting the charm process

Change-Id: I24aea9d29258e7d5a36d22a365eeb8f713cbab35
Signed-off-by: Adam Israel <adam.israel@canonical.com>

README.md

+# Juju Charm usage and development
+
+This document is intended to provide a brief overview of the components included
+in this repository as well as recommendations for how to develop, build, and
+publish charms.
+
+Please read the [develper geting started guide](https://jujucharms.com/docs/2.0/developer-getting-started) before proceeding.
+
+## Directory structure
+
+```
+.
+├── builds
+│   └── vpe-router
+├── interfaces
+├── layers
+│   └── vpe-router
+└── module-blueprints
+```
+
+The source code of a charm is referred to as a "layer". This layer is compiled
+into a charm and placed in the `builds/` directory. Interfaces, currently
+unused in this context, extend relationships between applications.
+
+## Development workflow
+### Prepare your build environment
+```
+# Source the environment variables JUJU_REPOSITORY, INTERFACE_PATH, and
+# LAYER_PATH, which are needed to build a charm. You could also place these
+# in your $HOME/.bashrc
+$ source juju-env.sh
+```
+#### Install the `charm` command, either via apt:
+
+```
+$ sudo apt install charm
+```
+
+or with [snap](http://snapcraft.io/)
+
+```
+$ snap install charm --edge
+```
+
+To build a charm, simply run `charm build` inside of a layer.
+```
+$ cd $LAYER_PATH/vpe-router
+$ charm build
+$ charm deploy $JUJU_REPOSITORY/builds/vpe-router
+```
+
+## Publishing to jujucharms.com
+
+Publishing to the Juju Charm store requires a launchpad login. With that, login
+to [jujucharms.com](http://www.jujucharms.com/).
+
+Next, you'll use the charm command to publish your compiled charm. This will
+put the charm into the store where it can be used by anyone with access.
+
+For example, if I wanted to publish the latest version of the vpe-router charm:
+
+# Step 1: Upload the charm to the "unpublished" channel
+```
+$ cd $JUJU_REPOSITORY/builds
+$ charm push vpe-router/ cs:~aisrael/vpe-router
+url: cs:~aisrael/vpe-router-0
+channel: unpublished
+```
+
+# There are four channels to release a charm: edge, beta, candidate, and stable
+```
+$ charm release cs:~aisrael/vpe-router-0 --channel=edge
+url: cs:~aisrael/vpe-router-0
+channel: edge
+```
+The charm can then be deployed directly from the charm store:
+```
+$ juju deploy cs:~aisrael/vpe-router --channel=edge
+```