Go on with implementing assertion methods listed on README.md

[csparpa]

As per title

Each new assertion method should:

• have a companion "negated" assertion method. If you implement is_xyz() method, then you should also implement a is_not_xyz() method alongside
• have at least one unit test

[dowenb]

is_uuid1() is going to be fun, because the RFC States:

Apart from determining whether the timestamp portion of the UUID
is in the future and therefore not yet assignable, there is no
mechanism for determining whether a UUID is 'valid'.

[dowenb]

Found something that might save me:
https://stackoverflow.com/questions/19989481/how-to-determine-if-a-string-is-a-valid-v4-uuid

going to give this a go