Change default build mode to install separate libdynd
Merge pull request #84 from mwiebe/default_install

Change default build mode to install separate libdynd
Make arrfunc_from_property return immutable arrfunc
Update fn getting arrfunc from assignment
Don't need errmode for make_arrfunc_from_property
Expose nd::arrfunc through the cython layer
Use static instances for date/time/datetime types as well
Make the arrfunc wrapper class a subclass of array