is_numeric to handle Index and Series type

[ajpotts]

is_numeric, is_float, and is_int to handle Index and Series type.

In [5]: i = ak.Index(ak.array([1, 2, 3]))

In [6]: from arkouda.util import is_numeric

In [7]: i = ak.Index(ak.array([1, 2, 3]))

In [8]: is_numeric(i)
Out[8]: True

In [9]: s = ak.Series(ak.array(["a","b","c"]), index=ak.array([1, 2, 3]))

In [10]: is_numeric(s)
Out[10]: False