Remove the unnecessary dependency: numpy

[MrLYC]

I noticed that jsonsubschema introduced numpy to create a specialized branch of support. In fact, this is unnecessary because Python already provides a simpler implementation.

[codecov[bot]]

Codecov Report

Patch coverage: 100.00% and project coverage change: +0.01% :tada:

Comparison is base (9c84182) 76.54% compared to head (ff6bc10) 76.56%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #17 +/- ## ========================================== + Coverage 76.54% 76.56% +0.01% ========================================== Files 8 8 Lines 1390 1391 +1 Branches 413 413 ========================================== + Hits 1064 1065 +1 Misses 232 232 Partials 94 94 ``` | [Files Changed](https://app.codecov.io/gh/IBM/jsonsubschema/pull/17?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=IBM) | Coverage Δ | | |---|---|---| | [jsonsubschema/\_canonicalization.py](https://app.codecov.io/gh/IBM/jsonsubschema/pull/17?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=IBM#diff-anNvbnN1YnNjaGVtYS9fY2Fub25pY2FsaXphdGlvbi5weQ==) | `93.68% <100.00%> (+0.03%)` | :arrow_up: |

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[shinnar]

Hi @MrLYC ! Thanks for submitting this PR, it looks good to me. In order to merge it in, we need a signed DCO: https://github.com/IBM/jsonsubschema/blob/master/DCO1.1.txt This just certifies that the code changes are original and that you are allowed and willing to license them under the Apache-2.0 license

[MrLYC]

Done, looking forward to the release of the new version.

[hirzel]

Dear @MrLYC , thank you for your contribution! Could you please email me a copy of the signed DCO at hirzel@us.ibm.com ?

[MrLYC]

@hirzel I have sent an email, is the format and content correct?

[hirzel]

Yes, received with thanks!