Added README.md

README.md

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+# Circular iterator (Citerate)
+
+Bi-dimensional matrix iterator starting from any point (i, j), going layer by layer around the starting coordinates.
+
+## Usage
+
+    pip install citerate
+
+As of __14 july 2021__ it contains one method `citerator`
+
+    from citerate import citerator
+
+## Examples
+
+Using the example data set:
+
+    CLOCKWISE_SET = [
+        [10, 11, 12, 13, 14],
+        [25, 2,  3,  4,  15],
+        [24, 9,  1,  5,  16],
+        [23, 8,  7,  6,  17],
+        [22, 21, 20, 19, 18],
+    ]
+
+To iterate over the set layer by layer starting from coordinates (i=2, j=2), which corresponds to the value 1 and print each layer of values.
+
+    for layer in citerate.citerator(CLOCKWISE_SET, i = 2, j = 2):
+        print(layer)
+
+Outputs:
+
+    [1]
+    [2, 3, 4, 5, 6, 7, 8, 9]
+    [10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25]
+
+# Footnotes
+
+- It is NOT mandatory to iterate starting from the central coordinates or for the matrix to be uniform.
+- It HAS to be bi-dimenstional and consist of "list of lists".