Add README.md

README.md

+## Install
+
+```bash
+git clone
+
+```
+
+
+# Usage
+
+### Create an image from .ctl file with command line
+
+```bash
+python -m plot_ctl --file=tests/data/mmsst.ctl --var=sst --tnum=0 --output=sst.png
+
+```
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