README: updating for the new version

Signed-off-by: Vincent Batts <vbatts@hashbangbash.com>

README.md

@@ -1,9 +1,46 @@
 # BuildSourceImage
-Tool to build a source image based on an existing OCI image
-
-
-This script uses BUILDAH to build source code container images based on
-existing OCI images.
 
+Tool to build a source image.
 The goal is to make retrieving the source code used to make a container image
 easier for users to obtain, using the standard OCI protocols and image formats.
+
+## Usage
+
+```bash
+$> ./BuildSourceImage.sh -h
+BuildSourceImage.sh version 0.1
+Usage: BuildSourceImage.sh [-D] [-b <path>] [-c <path>] [-e <path>] [-r <path>] [-o <path>] [-i <image>] [-p <image>] [-l] [-d <drivers>]
+
+       -b <path>        base path for source image builds
+       -c <path>        build context for the container image. Can be provided via CONTEXT_DIR env variable
+       -e <path>        extra src for the container image. Can be provided via EXTRA_SRC_DIR env variable
+       -s <path>        directory of SRPMS to add. Can be provided via SRPM_DIR env variable
+       -o <path>        output the OCI image to path. Can be provided via OUTPUT_DIR env variable
+       -d <drivers>     enumerate specific source drivers to run
+       -l               list the source drivers available
+       -i <image>       image reference to fetch and inspect its rootfs to derive sources
+       -p <image>       push source image to specified reference after build
+       -D               debuging output. Can be set via DEBUG env variable
+       -h               this usage information
+       -v               version
+
+```
+
+It also nicely usable inside a container
+```bash
+$> buildah build-using-dockerfile -t containers/buildsourceimage .
+```
+
+## Examples
+
+* Building from a fetched reference [![asciicast](https://asciinema.org/a/266340.svg)](https://asciinema.org/a/266340)
+* Building from a directory of src.rpms: [![asciicast](https://asciinema.org/a/266341.svg)](https://asciinema.org/a/266341)
+* Building from a directory of src.rpms and pushing it to a simple registry: [![asciicast](https://asciinema.org/a/266343.svg)](https://asciinema.org/a/266343)
+
+## Use Cases
+
+* Build a source image from an existing container image by introspection
+* Build a source code image from a collection of known `.src.rpm`'s
+* Include additional build context into the source image
+* Include extra sources use
+