Add example output to readme

Author: milliams

README.rst

@@ -3,3 +3,48 @@ plotlib
 
 ``plotlib`` is a generic data visualisation and plotting library for Rust.
 It is currently in the very early stages of development.
+
+It can currently produce scatter plot and histograms,
+rendering them as either SVG or plain text.
+
+The API is still very much in flux and is subject to change.
+
+For example, code like:
+
+.. code-block:: rust
+
+    extern crate plotlib;
+    use plotlib::scatter::Scatter;
+    use plotlib::scatter;
+    use plotlib::view::View;
+    use plotlib::plot::Plot;
+
+    fn main() {
+        // Scatter plots expect a list of pairs
+        let data1 = [(-3.0, 2.3), (-1.6, 5.3), (0.3, 0.7), (4.3, -1.4), (6.4, 4.3), (8.5, 3.7)];
+        // We create our scatter plot from the data
+        let s1 = Scatter::from_vec(&data1)
+            .style(scatter::Style::new()
+                .marker(scatter::Marker::Square) // setting the marker to be a square
+                .colour("#DD3355")); // and a custom colour
+
+        // We can plot multiple data sets in the same view
+        let data2 = [(-1.4, 2.5), (7.2, -0.3)];
+        let s2 = Scatter::from_vec(&data2)
+            .style(scatter::Style::new() // uses the default marker
+                .colour("#35C788")); // and a different colour
+
+        // The 'view' describeswhat set of data is drawn
+        let v = View::new()
+            .add(&s1)
+            .add(&s2)
+            .x_range(-5., 10.)
+            .y_range(-2., 6.);
+
+        // A plot with a single view is then saved to an SVG file
+        Plot::single(&v).save("scatter.svg");
+    }
+
+will produce output like:
+
+.. figure:: scatter.png