Merge pull request #12 from goldaxe/master

Correct text about exclusiveMaximum
rename `BUILD` to account for OSX

* OSX uses a case-insensitive filesystem so it cannot differentiate between a file named `BUILD` and a directory named `build/`.  Moving the BUILD file to BUILD.md means we can actually build the output under OSX
Merge pull request #14 from daveworth/make_build_work_on_OSX

rename `BUILD` to account for OSX