Attempt to implement class model below high-level HDF5

Does not work presently because setting instance attributes on __init__
triggers meta-method index, which is problematic.
Use getattrib and setattrib to work around infinite recursion
Expose a big flaw in the class model: method resolution goes not recurse
High-level HDF5 now works with class model
Remember to close files at end of unit tests
Merge branch 'master' into newclass

Conflicts:
	LuaHDF5.lua
Fix minor bug in File.__init__, forgot opts argument
Merge branch 'master' into newclass

Conflicts:
	LuaHDF5.lua