Thread Safe Attributes (attributes which can be shared across threads)

Added a ThreadSafeAttributes class which when inherited from will provide new
class level syntax for building thread safe attributes. At the class level you
would write _attributes = ['attr1', 'attr2', 'attr3'] to produce the thread
safe attributes, attr1, attr2 and attr3. (Under the hood these attributes
are actually properties of a small deque ring buffer of size 1.) To see more
about this feature reference the recipes section of the miros project at tag
v4.1.3 or later.