Write basic unit tests for the memory allocator

[colinbdclark]

While SIgnaletic's memory allocator is provided by a third party (Matt Conte's TLSF), it would nonetheless be a good idea to write some basic tests for our wrapper of it (star_Allocator) so that it will be easier to switch to a different implementation in the future if necessary (e.g. https://github.com/pavel-kirienko/o1heap).