requirements.txt => requirements_dev.txt, w/ min ver, not exact

requirements.txt

-appnope==0.1.0
-backcall==0.1.0
-bleach==2.1.4
-cycler==0.10.0
-decorator==4.3.0
-defusedxml==0.5.0
-entrypoints==0.2.3
-graphviz
-html5lib==1.0.1
-ipykernel==4.9.0
-ipympl==0.2.1
-ipython==6.5.0
-ipython-genutils==0.2.0
-ipywidgets==7.4.1
-jedi==0.12.1
-Jinja2==2.10
-jsonschema==2.6.0
-jupyter==1.0.0
-jupyter-client==5.2.3
-jupyter-console==5.2.0
-jupyter-core==4.4.0
-kiwisolver==1.0.1
-MarkupSafe==1.0
-matplotlib==2.2.3
-mistune==0.8.3
-nbconvert==5.4.0
-nbformat==4.4.0
-notebook==5.6.0
-numpy==1.15.1
-pandas==0.23.4
-pandocfilters==1.4.2
-parso==0.3.1
-pexpect==4.6.0
-pickleshare==0.7.4
-prometheus-client==0.3.1
-prompt-toolkit==1.0.15
-ptyprocess==0.6.0
-Pygments==2.2.0
-pyparsing==2.2.0
-python-dateutil==2.7.3
-pytz==2018.5
-pyzmq==17.1.2
-qtconsole==4.4.1
-scikit-learn==0.19.2
-scipy==1.1.0
-seaborn==0.9.0
-Send2Trash==1.5.0
-simplegeneric==0.8.1
-six==1.11.0
-terminado==0.8.1
-testpath==0.3.1
-tornado==5.1
-traitlets==4.3.2
-wcwidth==0.1.7
-webencodings==0.5.1
-widgetsnbextension==3.4.1

requirements_dev.txt

+appnope>=0.1.0
+backcall>=0.1.0
+bleach>=2.1.4
+cycler>=0.10.0
+decorator>=4.3.0
+defusedxml>=0.5.0
+entrypoints>=0.2.3
+graphviz
+html5lib>=1.0.1
+ipykernel>=4.9.0
+ipympl>=0.2.1
+ipython>=6.5.0
+ipython-genutils>=0.2.0
+ipywidgets>=7.4.1
+jedi>=0.12.1
+Jinja2>=2.10
+jsonschema>=2.6.0
+jupyter>=1.0.0
+jupyter-client>=5.2.3
+jupyter-console>=5.2.0
+jupyter-core>=4.4.0
+kiwisolver>=1.0.1
+MarkupSafe>=1.0
+matplotlib>=2.2.3
+mistune>=0.8.3
+nbconvert>=5.4.0
+nbformat>=4.4.0
+notebook>=5.6.0
+numpy>=1.15.1
+pandas>=0.23.4
+pandocfilters>=1.4.2
+parso>=0.3.1
+pexpect>=4.6.0
+pickleshare>=0.7.4
+prometheus-client>=0.3.1
+prompt-toolkit>=1.0.15
+ptyprocess>=0.6.0
+Pygments>=2.2.0
+pyparsing>=2.2.0
+python-dateutil>=2.7.3
+pytz>=2018.5
+pyzmq>=17.1.2
+qtconsole>=4.4.1
+scikit-learn>=0.19.2
+scipy>=1.1.0
+seaborn>=0.9.0
+Send2Trash>=1.5.0
+simplegeneric>=0.8.1
+six>=1.11.0
+terminado>=0.8.1
+testpath>=0.3.1
+tornado>=5.1
+traitlets>=4.3.2
+wcwidth>=0.1.7
+webencodings>=0.5.1
+widgetsnbextension>=3.4.1