Merge pull request #14 from edx/clee/profile_name

added note for profile_name convention

README.md

 edx-val
 =======
+
+Note:
+    The naming convetion for the `profile_name` in `Profile` objects will be the
+    medium of the profile (a-z), an underscore, and then the quality (a-z).
+
+    Examples:
+    desktop_high
+    mobile_medium
+    somethingelse_low