Fix invalid character exception in bulk add

This fixes the bug whereby "<" raised an exception. See https://www.pivotaltracker.com/story/show/64466526.

The first way I tried encoded "<" and ">" as HTML entities due to URI.parse not parsing and encoding them itself, which worked fine and fixed the exception, but wasn't very user-friendly.
Next, it was decided not to encode them as URI::BLURI (part of optic14n) deals with "<" and ">" characters etc. Now the exception that occurred upon only entering "<" into the input box is handled and actual characters "<" and ">" are visible in paths.