Add example with all the possible syntax.

examples/all.rs

@@ -0,0 +1,36 @@
+#[macro_use]
+extern crate error_chain;
+
+pub mod inner {
+    error_chain! {}
+}
+
+#[cfg(feature = "a_feature")]
+pub mod feature {
+    error_chain! {}
+}
+
+error_chain! {
+    // Types generated by the macro. If empty of absent, it defaults to
+    //     Error, ErrorKind, Result;
+    types {
+        // With custom names:
+        MyError, MyErrorKind, MyResult;
+        // Without the `Result` wrapper:
+        //     Error, ErrorKind;
+    }
+
+    // Automatic bindings to others error types generated by `error_chain!`.
+    links {
+        inner::Error, Inner;
+        // Attributes can be added at the end of the declaration.
+        feature::Error, Feature, #[cfg(feature = "a_feature")];
+    }
+
+    // Bindings to types implementing std::error::Error.
+    foreign_links {
+        ::std::io::Error, Io;
+    }
+}
+
+fn main() {}