html5lib parser failing due to less than symbol in XML files

[krisbukovi]

243 Errors such as "Invalid HTML tag name", "Invalid tag name", "Empty tag name", "Invalid namespace URI" are occurring as a result of "<" symbols that are mistaken for the beginning of an XML tag by the html5lib parser.

Part of the problem is due to uncaught latex formulas that we remove using a regular expression. See 2015GeoJI.200.1466Z for example.

A number of these errors are slightly more difficult to resolve as they occur from images. See this google doc for more details.