New Rule: Hex

[CSenshi]

Rule Name: Hex

Rule Description: The field under validation must be a hexadecimal number

Rule Usage Example:

reqs = {"data" : "A1B2c3"}
rule = {"data" : "hex"}
validate(reqs, rule) # True

reqs = {"data" : "0xA1b2C3"}
rule = {"data" : "hex"}
validate(reqs, rule) # True

reqs = {"data" : "abcdefgh"}
rule = {"data" : "hex"}
validate(reqs, rule) # False, It fails because 'g','h' are not in hexadecimal

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Before contributing please review RULES.md (check for duplication), also check CONTRIBUTING.md for more details :100: