chore: update links to examples in README

Links now include the fully qualified domain as well as the version.
This will make them work in docs.rs and make sure readers are looking at code which is consistent with the latest version available.

README.md

@@ -50,8 +50,8 @@ cargo run --example termion_demo --release -- --tick-rate 200
 
 where `tick-rate` is the UI refresh rate in ms.
 
-The UI code is in [examples/demo/ui.rs](examples/demo/ui.rs) while the
-application state is in [examples/demo/app.rs](examples/demo/app.rs).
+The UI code is in [examples/demo/ui.rs](https://github.com/fdehau/tui-rs/blob/v0.15.0/examples/demo/ui.rs) while the
+application state is in [examples/demo/app.rs](https://github.com/fdehau/tui-rs/blob/v0.15.0/examples/demo/app.rs).
 
 Beware that the `termion_demo` only works on Unix platforms. If you are a Windows user,
 you can see the same demo using the `crossterm` backend with the following command:
@@ -71,16 +71,16 @@ cargo run --example crossterm_demo --no-default-features --features="crossterm"
 
 The library comes with the following list of widgets:
 
-  * [Block](examples/block.rs)
-  * [Gauge](examples/gauge.rs)
-  * [Sparkline](examples/sparkline.rs)
-  * [Chart](examples/chart.rs)
-  * [BarChart](examples/barchart.rs)
-  * [List](examples/list.rs)
-  * [Table](examples/table.rs)
-  * [Paragraph](examples/paragraph.rs)
-  * [Canvas (with line, point cloud, map)](examples/canvas.rs)
-  * [Tabs](examples/tabs.rs)
+  * [Block](https://github.com/fdehau/tui-rs/blob/v0.15.0/examples/block.rs)
+  * [Gauge](https://github.com/fdehau/tui-rs/blob/v0.15.0/examples/gauge.rs)
+  * [Sparkline](https://github.com/fdehau/tui-rs/blob/v0.15.0/examples/sparkline.rs)
+  * [Chart](https://github.com/fdehau/tui-rs/blob/v0.15.0/examples/chart.rs)
+  * [BarChart](https://github.com/fdehau/tui-rs/blob/v0.15.0/examples/barchart.rs)
+  * [List](https://github.com/fdehau/tui-rs/blob/v0.15.0/examples/list.rs)
+  * [Table](https://github.com/fdehau/tui-rs/blob/v0.15.0/examples/table.rs)
+  * [Paragraph](https://github.com/fdehau/tui-rs/blob/v0.15.0/examples/paragraph.rs)
+  * [Canvas (with line, point cloud, map)](https://github.com/fdehau/tui-rs/blob/v0.15.0/examples/canvas.rs)
+  * [Tabs](https://github.com/fdehau/tui-rs/blob/v0.15.0/examples/tabs.rs)
 
 Click on each item to see the source of the example. Run the examples with with 
 cargo (e.g. to run the demo `cargo run --example demo`), and quit by pressing `q`.