Add docs for identify command

docs/identify.md

@@ -0,0 +1,26 @@
+# Identify
+
+`please identify` can identify some common data formats and, give some data on standard input, will print out the format used.
+
+Currently, `identify` can reliably tell the difference between:
+
+* JSON
+* YAML
+* XML
+* MIME messages
+
+## Usage
+
+    please identify
+
+    Identifies the format of the structured data on standard input
+
+## Examples
+
+Identifying some data:
+
+    $ echo '{"this":{"is":["some","json"],"that":"we"},"will":"parse"}' | please identify
+    json
+
+    $ echo -e "this:\n  looks: like\n  some: yaml" | please identify
+    yaml