branch for working on struct
Minimize method calls for speed
Update to v0.4.0
 - add first/last/firstOrDefault/lastOrDefault methods and unit tests
cleanup
BF: randomize could fail with column
avoid cellfun/arrayfun consistently
Update to v0.5.0
 - documentation
 - select() throws error when uniform output fails
 - select() accepts strings that are function names in addition to handles
 - sort() allows selecting ascending or descending order
 - overload subsref for direct array placement
 - make some functions private to class