Added file uploading support, v0.5.2

- Added example `file_bot.py`
- Added *.tmp to .gitignore
- Added CTX_FILE_SIZE, CTX_FILE_MIME and CTX_FILE_NAME
- Added MessageHasFile filter
- Added `send_file` and `send_file_bytes` for ClientSender and Bot

.gitignore

@@ -5,4 +5,5 @@ session_storage/
 dist/
 *.egg-info/
 *.swp
-*.swo
+*.swo
+*.tmp