Default log level name style to use bright black

Black text is not visible on black terminals. Using black color as
a default might not be visible on many setups out there (a lot of
developers use black backgrounds). Using dark gray color (bright black)
seems like a reasonable compromise if log level is chosen to be dark by
default.

Author: arkq

coloredlogs/__init__.py

@@ -231,7 +231,7 @@
 DEFAULT_FIELD_STYLES = dict(
     asctime=dict(color='green'),
     hostname=dict(color='magenta'),
-    levelname=dict(color='black', bold=True),
+    levelname=dict(color='black', bold=True, bright=True),
     name=dict(color='blue'),
     programname=dict(color='cyan'),
     username=dict(color='yellow'),