trezor.io: rework for new structure

src/trezor/__init__.py

@@ -1 +1,2 @@
 import trezorconfig as config
+import trezorio as io

src/trezor/io.py

@@ -1 +0,0 @@
-from trezorio import SDCard

tests/test_trezor.io.py

@@ -0,0 +1,12 @@
+from common import *
+
+from trezor import io
+
+class TestIo(unittest.TestCase):
+
+    def test_sdcard(self):
+        sd = io.SDCard()
+        sd.present()
+
+if __name__ == '__main__':
+    unittest.main()