Bump psutil from 5.3.1 to 5.6.6

Bumps [psutil](https://github.com/giampaolo/psutil) from 5.3.1 to 5.6.6.
- [Release notes](https://github.com/giampaolo/psutil/releases)
- [Changelog](https://github.com/giampaolo/psutil/blob/master/HISTORY.rst)
- [Commits](giampaolo/psutil@release-5.3.1...release-5.6.6)

Signed-off-by: dependabot[bot] <[email protected]>

requirements.txt

@@ -4,42 +4,42 @@
 #
 #    pip-compile --output-file requirements.txt requirements.in
 #
-ansiconv==1.0.0
+ansiconv==1.0.0           # via -r requirements.in
 certifi==2017.7.27.1      # via requests
 chardet==3.0.4            # via requests
-colorlog==3.1.0
+colorlog==3.1.0           # via -r requirements.in
 coverage==4.4.1           # via pytest-cov
-croniter==0.3.19
+croniter==0.3.19          # via -r requirements.in
 decorator==4.1.2          # via ipython, traitlets
-django-crispy-forms==1.6.1
-django==1.11.6
+django-crispy-forms==1.6.1  # via -r requirements.in
+django==1.11.6            # via -r requirements.in
 idna==2.6                 # via requests
 ipython-genutils==0.2.0   # via traitlets
-ipython==6.2.1
+ipython==6.2.1            # via -r requirements.in
 jedi==0.11.0              # via ipython
 parso==0.1.0              # via jedi
 pexpect==4.2.1            # via ipython
 pickleshare==0.7.4        # via ipython
 prompt-toolkit==1.0.15    # via ipython
-psutil==5.3.1
+psutil==5.6.6             # via -r requirements.in
 ptyprocess==0.5.2         # via pexpect
 py==1.4.34                # via pytest
-pyfirmata==1.0.3
+pyfirmata==1.0.3          # via -r requirements.in
 pygments==2.2.0           # via ipython
-pyinotify==0.9.6
+pyinotify==0.9.6          # via -r requirements.in
 pyserial==3.4             # via pyfirmata
-pytest-cov==2.5.1
-pytest-pycharm==0.4.0
-pytest==3.2.3
+pytest-cov==2.5.1         # via -r requirements.in
+pytest-pycharm==0.4.0     # via -r requirements.in
+pytest==3.2.3             # via -r requirements.in, pytest-cov, pytest-pycharm
 python-dateutil==2.6.1    # via croniter
 pytz==2017.2              # via django
-raven==6.2.1
-requests==2.18.4
-rpio==0.10.0
+raven==6.2.1              # via -r requirements.in
+requests==2.18.4          # via -r requirements.in
+rpio==0.10.0              # via -r requirements.in
 simplegeneric==0.8.1      # via ipython
 six==1.11.0               # via prompt-toolkit, python-dateutil, traitlets
-tornado==4.5.2
+tornado==4.5.2            # via -r requirements.in
 traitlets==4.3.2          # via ipython
-traits==4.6.0
+traits==4.6.0             # via -r requirements.in
 urllib3==1.22             # via requests
 wcwidth==0.1.7            # via prompt-toolkit