Merge pull request #125 from metafacture/123-documentAPI

Add a section in README to document the HTTP API.

README.md

@@ -168,3 +168,12 @@ retain(id, title, author)
 The parameter values must be URL-encoded so the URL looks like this:
 
 http://localhost:3000/process?flux=inputFile%0A%7Copen-file%0A%7Cas-lines%0A%7Cdecode-formeta%0A%7Cfix%28transformationFile%29%0A%7Cencode-xml%28rootTag%3D%22collection%22%29%0A%7Cprint%0A%3B&transformation=move_field%28_id%2C+id%29%0Amove_field%28a%2C+title%29%0Apaste%28author%2C+b.v%2C+b.n%2C+%27~aus%27%2C+c%29%0Aretain%28id%2C+title%2C+author%29&data=1%7Ba%3A+Faust%2C+b+%7Bn%3A+Goethe%2C+v%3A+JW%7D%2C+c%3A+Weimar%7D%0A2%7Ba%3A+R%C3%A4uber%2C+b+%7Bn%3A+Schiller%2C+v%3A+F%7D%2C+c%3A+Weimar%7D
+
+## Use Metafacture Playground API
+
+Beside the web application the Metafacture Playground provides a HTTP API to process workflows. All you need is to provide the workflow information as JSON parameters in your POST request.
+
+```
+curl -X POST https://test.metafacture.org/playground/process -H 'Content-Type: application/json' -d '{"data":"1{a: Faust, b {n: Goethe, v: JW}, c: Weimar}\n2{a: Räuber, b {n: Schiller, v: F}, c: Weimar}","flux":"inputFile\n|open-file\n|as-lines\n|decode-formeta\n|fix(transformationFile)\n|encode-xml(rootTag=\"collection\")\n|print\n;","transformation":"move_field(_id, id)\nmove_field(a, title)\npaste(author, b.v, b.n, \"~aus\", c)\nretain(id, title,
+ author)\n"}'
+```