SPARK-1846 Ignore logs directory in RAT checks

https://issues.apache.org/jira/browse/SPARK-1846

Author: Andrew Ash <[email protected]>

Closes #793 from ash211/SPARK-1846 and squashes the following commits:

3f50db5 [Andrew Ash] SPARK-1846 Ignore logs directory in RAT checks
(cherry picked from commit 3abe2b7)

Signed-off-by: Patrick Wendell <[email protected]>

Author: ash211

.rat-excludes

@@ -48,3 +48,4 @@ dist/*
 .*out
 .*ipr
 .*iws
+logs