Update psutil to 5.5.1

[pyup-bot]

This PR updates psutil from 5.5.0 to 5.5.1.

Changelog

5.5.1

=====

2019-02-15

**Enhancements**

- 1348_: [Windows] on Windows >= 8.1 if Process.cmdline() fails due to
ERROR_ACCESS_DENIED attempt using NtQueryInformationProcess +
ProcessCommandLineInformation. (patch by EccoTheFlintstone)

**Bug fixes**

- 1394_: [Windows] Process.exe() returns "[Error 0] The operation completed
successfully" when Python process runs in "Virtual Secure Mode".
- 1402_: psutil exceptions' repr() show the internal private module path.
- 1408_: [AIX] psutil won't compile on AIX 7.1 due to missing header.  (patch
by Arnon Yaari)

Links

• PyPI: https://pypi.org/project/psutil
• Changelog: https://pyup.io/changelogs/psutil/
• Repo: https://github.com/giampaolo/psutil