implement __sizeof__ for tinyarray

A new method `object_size` is added to the Array template class, which
calculates the total size of the Python object in bytes.  The function
`size_of` then wraps this method and provides the necessary interface
for a Python method object.
2 jobs for feature/sizeof
Status Name Job ID Coverage
failed python2 #352


passed python3 #353


Name Stage Failure
python2 Test There is an unknown failure, please try again

git branch <new-branch-name> ea26418

HEAD is now at ed42e40... implement __sizeof__ for tinyarray

$ python2 build_ext -i
/bin/bash: line 20: python2: command not found

ERROR: Build failed: exit code 1