update readme

README.md

@@ -1,16 +1,34 @@
 # transbeam
 
-A low-frills low-latency file drop server
+A low-latency file drop server
+
+## features
+
+- One-to-many transfer of large files
+- Simple web UI for sender and receivers
+- Receivers can begin downloading *immediately*, without needing to
+  wait for the upload to finish
+- Receivers can also download after the upload is complete and the
+  sender has gone offline
+- Easy to send multiple files at once - they're bundled into a zip
+  file for receivers, with zero compression so extraction is quick
+- Sanitizes filenames
+- Fires a laser beam that turns you trans
+
+## configuration
+
+transbeam is configured with the following environment variables:
+- `STORAGE_DIR`: path where uploaded files should be stored (default: `./storage`)
+- `STATIC_DIR`: path where the web app's static files live (default: `./static`)
+- `PORT`: port to listen on localhost for http requests (default: 8080)
 
 ## installation
 
+## configuration
 ## todo
 
-- [ ] file uploading
 - [ ] real-time file downloading
 - [ ] upload progress bar
 - [ ] uploader auth
 - [ ] downloader auth
-- [ ] sanitize filenames
-- [ ] make sure upload errors are passed along to downloaders in a halfway reasonable way
 - [ ] delete uploads after a while