Adds more descriptive READMEs

Resolves #2

README.md

@@ -1,6 +1,30 @@
-# No App Cloud Native Buildpack
+# Build Plan Cloud Native Buildpack
+This buildpack is meant to be used to write a Build Plan generated from the contents of an `plan.toml` in the base of the application directory. The `plan.toml` is meant to reflect the contents of [Build Plan (TOML)](https://github.com/buildpacks/spec/blob/master/buildpack.md#build-plan-toml) that is currently supported by `packit`.
+
+## Usage
+
 To package this buildpack for consumption:
+
 ```
 $ ./scripts/package.sh
 ```
-This builds the buildpack's Go source using GOOS=linux by default. You can supply another value as the first argument to package.sh.
+
+This builds the buildpack's Go source using `GOOS=linux` by default. You can
+supply another value as the first argument to `package.sh`.
+
+## `plan.toml`
+
+```toml
+[[provides]]
+name = "<dependency name>"
+
+[[requires]]
+name = "<dependency name>"
+version = "<dependency version>"
+
+[requires.metadata]
+# buildpack-specific data
+```
+
+If you are looking for concrete definitions on what these fields do inside of `packit` you can check the documentation [here](https://godoc.org/github.com/paketo-buildpacks/packit#BuildPlan). For the definition from the Cloud Native Buildpack specification itself you can check out the documentation [here](https://godoc.org/github.com/paketo-buildpacks/packit#BuildPlan).
+To package this buildpack for consumption: