Separate html/csv output functions into html_writer.py

* also suppress some pylint warnings

Test: warn.py --url=http://cs/android --separator='?l=' build.log > warnings.html
Test: warn.py --gencsv build.log > warnings.csv
Change-Id: I497dbb7496ca21470ba33db03eedb27f5e8f1e96
diff --git a/tools/warn/tidy_warn_patterns.py b/tools/warn/tidy_warn_patterns.py
index 036e2bb..5416cb2 100644
--- a/tools/warn/tidy_warn_patterns.py
+++ b/tools/warn/tidy_warn_patterns.py
@@ -16,8 +16,8 @@
 """Warning patterns for clang-tidy."""
 
 # pylint:disable=relative-beyond-top-level
-from .cpp_warn_patterns import compile_patterns
 # pylint:disable=g-importing-member
+from .cpp_warn_patterns import compile_patterns
 from .severity import Severity