Add sample/README to give sample usage.

README.md

@@ -9,12 +9,13 @@ depend on the official release binaries provided by the Pandoc project.
 
 # Using these rules
 
+## Set up your workspace
+
 Add the following to your `WORKSPACE` file:
 
 ```python
 http_archive(
     name = "bazel_pandoc",
-    sha256 = "<checksum>",
     strip_prefix = "bazel-pandoc-<release>",
     url = "https://github.com/ProdriveTechnologies/bazel-pandoc/archive/v<release>.tar.gz",
 )
@@ -24,6 +25,8 @@ load("@bazel_pandoc//:repositories.bzl", "pandoc_repositories")
 pandoc_repositories()
 ```
 
+## Use the `pandoc` rule in BUILD files
+
 You can then add directives along these lines to your `BUILD.bazel` files:
 
 ```python

sample/README.md

@@ -0,0 +1,18 @@
+# Sample usage of the pandoc rule
+
+Once you have set up your workspace,
+you can generate the [README](../README.md) in a multitude of formats.
+
+For instance:
+
+```sh
+bazel build @bazel_pandoc//sample:readme_plain
+bazel build @bazel_pandoc//sample:readme_html
+bazel build @bazel_pandoc//sample:readme_epub
+```
+
+You can also produce the README in all formats know to the rule:
+
+```sh
+bazel build @bazel_pandoc//sample/...
+```