Merge pull request #213 from abiogenesis-now/jyao/fix-premature-yaml-component-explanation

[docs] Fix premature claim of YAML support in components explanation

docs/concepts.md

@@ -66,7 +66,9 @@ Components can be as simple as a single Kubernetes resource (e.g. a Deployment)
 
 * Typically, **you autogenerate it** with the [`ks generate`](/docs/cli-reference/ks_generate.md) command. In this case, the manifest is expressed in a language called [Jsonnet](#jsonnet).
 
-* Alternatively, you can **manually drop in** a file. In this case, your manifest can be any one of YAML, JSON, or Jsonnet. Because all three languages are supported, *this approach allows you to introduce ksonnet to existing codebases without significant rewrites*.
+* Alternatively, you can **manually drop in** a file into `components/`. In this case, you can use either JSON or Jsonnet, as long the file is saved with the `*.jsonnet` extension. (JSON is a subset of Jsonnet so no other changes are needed. YAML is not currently supported, but you can use an open-source CLI tool such as [yaml2json](https://github.com/bronze1man/yaml2json) to convert from YAML to JSON).
+
+  *This approach allows you to introduce ksonnet to existing codebases*.
 
 How does the autogeneration process work? When you use `ks generate`, the component is generated from a *prototype*. The distinction between a component and a prototype is a bit subtle. If you are familiar with object oriented programming, you can roughly think of a prototype as a "class", and a component as its instantiation: