Added a simple readme

README.md

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+# An example of Flink Windows and Watermarks
+
+TODO
+
+## Running
+
+One window: `nc -l 60000`
+
+Other window: `sbt "run --hostname 127.0.0.1 --port 60000"`
+
+## Input
+
+_TODO_: EXPLAIN THIS
+
+1 window1
+2 window1
+2 window1
+20 window1
+29 window1
+31 window2
+45 window2
+21 window1
+
+
+## Output
+
+CREATE                    - window1 at 1s seen 1 times
+WATERMARK                 - moved to -9
+CREATE                    - window1 at 2s seen 1 times
+WATERMARK                 - moved to -8
+REDUCE                    - window1 at 1s seen 1 times + window1 at 2s seen 1 times, now window1 at 1s seen 2 times
+CREATE                    - window1 at 2s seen 1 times
+REDUCE                    - window1 at 1s seen 2 times + window1 at 2s seen 1 times, now window1 at 1s seen 3 times
+CREATE                    - window1 at 20s seen 1 times
+WATERMARK                 - moved to 10
+REDUCE                    - window1 at 1s seen 3 times + window1 at 20s seen 1 times, now window1 at 1s seen 4 times
+CREATE                    - window1 at 29s seen 1 times
+WATERMARK                 - moved to 19
+REDUCE                    - window1 at 1s seen 4 times + window1 at 29s seen 1 times, now window1 at 1s seen 5 times
+CREATE                    - window2 at 31s seen 1 times
+WATERMARK                 - moved to 21
+CREATE                    - window2 at 45s seen 1 times
+WATERMARK                 - moved to 35
+REDUCE                    - window2 at 31s seen 1 times + window2 at 45s seen 1 times, now window2 at 31s seen 2 times
+FIRING                    - window1 at 1s seen 5 times to 0, now window1 at 0s seen 5 times
+SINK                      - window1 at 0s seen 5 times
+CREATE                    - window1 at 21s seen 1 times
+REDUCE                    - window1 at 1s seen 5 times + window1 at 21s seen 1 times, now window1 at 1s seen 6 times
+FIRING                    - window1 at 1s seen 6 times to 0, now window1 at 0s seen 6 times
+SINK                      - window1 at 0s seen 6 times
+FIRING                    - window2 at 31s seen 2 times to 30, now window2 at 30s seen 2 times
+SINK                      - window2 at 30s seen 2 times
+