[Snyk] Fix for 2 vulnerabilities

Snyk has created this PR to fix one or more vulnerable packages in the `pip` dependencies of this project.

Changes included in this PR

Changes to the following files to upgrade the vulnerable dependencies to a fixed version:
- requirements.txt

⚠️ Warning

``` pandas 0.17.0 requires pytz, which is not installed. oceans 0.2.5 requires gsw, which is not installed. oceans 0.2.5 requires matplotlib, which is not installed. jupyter 1.0.0 requires qtconsole, which is not installed. jsonschema 3.2.0 requires pyrsistent, which is not installed. ```

Vulnerabilities that will be fixed

By pinning:

Severity	Priority Score (*)	Issue	Upgrade	Breaking Change	Exploit Maturity
	506/1000 Why? Recently disclosed, Has a fix available, CVSS 4.4	Open Redirect SNYK-PYTHON-NOTEBOOK-1041707	`notebook:` `5.7.10 -> 6.1.5`	No	No Known Exploit
	704/1000 Why? Has a fix available, CVSS 9.8	Information Exposure SNYK-PYTHON-REQUESTS-72435	`requests:` `2.8.1 -> 2.20`	No	No Known Exploit

(*) Note that the real score may have changed since the PR was raised.

Some vulnerabilities couldn't be fully fixed and so Snyk will still find them when the project is tested again. This may be because the vulnerability existed within more than one direct dependency, but not all of the effected dependencies could be upgraded.

Check the changes in this PR to ensure they won't cause issues with your project.

Note: You are seeing this because you or someone else with access to this repository has authorized Snyk to open fix PRs.

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MBARIMike / oxyfloat