Merge pull request #11 from dherrada/master

Fixed OSError from #9 using @maholli's code

Author: ladyada

adafruit_miniesptool.py

@@ -101,7 +101,7 @@ class miniesptool: # pylint: disable=invalid-name
     boards, so you can burn ESP firmware direct from the CPy disk drive. Handy
     when you have an ESP module wired to a board and need to upload new AT
     firmware. Its slow! Expect a few minutes when programming 1 MB flash."""
-    FLASH_WRITE_SIZE = 0x400
+    FLASH_WRITE_SIZE = 0x200
     FLASH_SECTOR_SIZE = 0x1000 # Flash sector size, minimum unit of erase.
     ESP_ROM_BAUD = 115200