Update requirements

Generated from pipenv with:

  $ pipenv lock -r > requirements.txt
  $ pipenv lock -r -d > requirements-dev.txt

requirements-dev.txt

@@ -1,25 +1,26 @@
 -i https://pypi.org/simple
-atomicwrites==1.2.1
+atomicwrites==1.3.0
 attrs==18.2.0
 backcall==0.1.0
-decorator==4.3.0
-flake8==3.6.0
+decorator==4.3.2
+entrypoints==0.3
+flake8==3.7.5
 ipython-genutils==0.2.0
 ipython==7.2.0
 jedi==0.13.2
 mccabe==0.6.1
 more-itertools==5.0.0
-parso==0.3.1
+parso==0.3.3
 pexpect==4.6.0 ; sys_platform != 'win32'
 pickleshare==0.7.5
 pluggy==0.8.1
-prompt-toolkit==2.0.7
+prompt-toolkit==2.0.8
 ptyprocess==0.6.0
 py==1.7.0
-pycodestyle==2.4.0
-pyflakes==2.0.0
+pycodestyle==2.5.0
+pyflakes==2.1.0
 pygments==2.3.1
-pytest==4.1.1
+pytest==4.2.0
 six==1.12.0
 traitlets==4.3.2
 wcwidth==0.1.7