Adds libxml++ to the list of dependencies. The Cyclus build requires it, but it hadn't been in the readme.
Boost capitalization matters on a mac. I've fixed this before, so I'm not sure why it's reappeared. I hope everyone can keep an eye on it and not change Boost back to BOOST.
adds comment
adds comment per review request by @gidden
Merge pull request #462 from katyhuff/libxml++_readme

Adds libxml++ to the list of dependencies in the readme
Merge pull request #463 from katyhuff/boost_includes

removes all uppercase boost call for use on a mac