binops for strings

[ajpotts]

Add binops :

• "<",
• "<=",
• "==",
• ">=",
• ">",
• "!="

for strings, similar to numpy:

In [6]: import numpy as np
In [7]: a = np.array(["a","b"])
In [8]: b = np.array(["a","c"])
In [9]: a < b
Out[9]: array([False,  True])