Unset executable bits on several files.

CONTRIBUTING.md, LICENSE, README.md, package.json,
sources/(us-ca-yolo, us-tx-denton).json
	-Remove executable permissions from files that don't have any
	need for them (they were added to all of the above files, except
	`sources/us-ca-yolo.json`, which was committed with them, in
	a864f8e).
Remove trailing whitespace in *.js; del swap file.

sources/us-ny.json~
	-Remove a swap file.

stats.js, test/sources.js
	-Remove trailing whitespace and superfluous empty lines.
Unset executable bits on two more files.

.gitignore, .travis.yml
	-Remove unnecessary executable permissions.
	-Missed these in 026e901.