only set CXX if it's undefined
possible fix for problems macs seem to have linking to this
-no-undefined --> --no-undefined (the later may be more universal)
ndhist finds hdf5 by looking for the executable
remove --no-undefined (for now)
ubuntu fix
Merge pull request #1 from dguest/mac

Mac branch should work fine on linux too, should make it master
cleanup attribute writers
Changed how axis info is serialized, attribute strings are UTF-8. Also lots of cleanup.
lots of documentation added, move Axis structure into another header.
added readme
got current