Test revealing StaticFileHandler path regression.

A bisect suggests that the regression was introduced in
3f04edf5546e388293d8d1d2f015ca74f8a93217
Merge remote-tracking branch 'wolever/fix-staticfile-serving' into merge

Conflicts:
	tornado/test/web_test.py
Avoid references to self.settings in StaticFileHandler instance methods.

This fixes support for secondary StaticFileHandlers configured separately
from the default static_path.

Changed the interfaces of some new-to-3.1 methods to avoid passing in
settings to class methods used in both class and instance contexts.

Closes #796.