add example usage to readme

README.md

@@ -1 +1,20 @@
-TODO
+# Usage
+
+```python
+from manga_ocr import MangaOcr
+
+mocr = MangaOcr()
+text = mocr('/path/to/img')
+```
+
+or
+
+```python
+import PIL.Image
+
+from manga_ocr import MangaOcr
+
+mocr = MangaOcr()
+img = PIL.Image.open('/path/to/img')
+text = mocr(img)
+```