Basic readme for usage

Author: implausible

README.md

@@ -1 +1,28 @@
-diff3
+# diff3
+
+## Usage
+```js
+var diff3Merge = require('diff3');
+var a = ['a', 'text', 'file'];
+var o = ['a', 'test', 'file'];
+var b = ['a', 'toasty', 'filtered', 'file'];
+var diff3 = diff3Merge(a, o, b);
+```
+
+## Output
+```JSON
+[{
+    "ok": ["a"]
+}, {
+    "conflict": {
+        "a": ["text"],
+        "aIndex": 1,
+        "o": ["test"],
+        "oIndex": 1,
+        "b": ["toasty", "filtered"],
+        "bIndex": 1
+    }
+}, {
+    "ok": ["file"]
+}]
+```