Make IO a static class instead of a singleton.

test/bool/equality.wren

@@ -1,23 +1,23 @@
-io.write(true == true)    // expect: true
-io.write(true == false)   // expect: false
-io.write(false == true)   // expect: false
-io.write(false == false)  // expect: true
+IO.write(true == true)    // expect: true
+IO.write(true == false)   // expect: false
+IO.write(false == true)   // expect: false
+IO.write(false == false)  // expect: true
 
 // Not equal to other types.
-io.write(true == 1)        // expect: false
-io.write(false == 0)       // expect: false
-io.write(true == "true")   // expect: false
-io.write(false == "false") // expect: false
-io.write(false == "")      // expect: false
+IO.write(true == 1)        // expect: false
+IO.write(false == 0)       // expect: false
+IO.write(true == "true")   // expect: false
+IO.write(false == "false") // expect: false
+IO.write(false == "")      // expect: false
 
-io.write(true != true)    // expect: false
-io.write(true != false)   // expect: true
-io.write(false != true)   // expect: true
-io.write(false != false)  // expect: false
+IO.write(true != true)    // expect: false
+IO.write(true != false)   // expect: true
+IO.write(false != true)   // expect: true
+IO.write(false != false)  // expect: false
 
 // Not equal to other types.
-io.write(true != 1)        // expect: true
-io.write(false != 0)       // expect: true
-io.write(true != "true")   // expect: true
-io.write(false != "false") // expect: true
-io.write(false != "")      // expect: true
+IO.write(true != 1)        // expect: true
+IO.write(false != 0)       // expect: true
+IO.write(true != "true")   // expect: true
+IO.write(false != "false") // expect: true
+IO.write(false != "")      // expect: true

test/bool/not.wren

@@ -1,3 +1,3 @@
-io.write(!true)    // expect: false
-io.write(!false)   // expect: true
-io.write(!!true)   // expect: true
+IO.write(!true)    // expect: false
+IO.write(!false)   // expect: true
+IO.write(!!true)   // expect: true

test/bool/to_string.wren

@@ -1,2 +1,2 @@
-io.write(true.toString)  // expect: true
-io.write(false.toString) // expect: false
+IO.write(true.toString)  // expect: true
+IO.write(false.toString) // expect: false

test/bool/type.wren

@@ -1,4 +1,4 @@
-io.write(true is Bool)      // expect: true
-io.write(true is Object)    // expect: true
-io.write(true is Num)       // expect: false
-io.write(true.type == Bool) // expect: true
+IO.write(true is Bool)      // expect: true
+IO.write(true is Object)    // expect: true
+IO.write(true is Num)       // expect: false
+IO.write(true.type == Bool) // expect: true