Merge branch 'master' of https://github.com/Microsoft/pxt-microbit

# Conflicts:
#	package.json

docs/js/sequence.md

@@ -1,6 +1,6 @@
-# Sequencing commands
+# Sequencing
 
-By calling one function after another, you can create an animation:
+By calling one function after another, in sequence, you can create an animation:
 
 ```typescript
 basic.showLeds(`
@@ -9,17 +9,47 @@ basic.showLeds(`
     . . # . .
     # . . . #
     . # # # .
-    `)
+    `);
 basic.showLeds(`
     . # . # .
     . . . . .
     . . . . .
     . # # # .
     # . . . #
-    `)
+    `);
 ```
 
-## The Semicolon
+### The semicolon 
 
-Coming soon...
+In JavaScript, the semicolon (;) is used to terminate (or end) a statement. However, in most
+cases, the semicolon is optional and can be omitted. So both code sequences below are 
+legal:
 
+```typescript
+basic.showNumber(1)  basic.showNumber(2)
+```
+
+```typescript
+basic.showNumber(1); basic.showNumber(2);
+```
+
+## The empty statement
+
+In JavaScript, there is the concept of an *empty statement*, which is whitespace followed by
+a semicolon in the context where a statement is expected.
+So, the following code is an infinite loop
+followed by a call to `showNumber` that will never execute:
+```typescript
+while(true) ;  basic.showNumber(1);
+```
+For the micro:bit, we don't allow a program to contain an empty statement, such as shown above. 
+If you really want an empty statement, you need to use curly braces to delimit an empty statement block:
+```typescript
+while(true) { } basic.showNumber(1);
+```
+
+[Read more](http://inimino.org/~inimino/blog/javascript_semicolons) about semicolons in JavaScript.
+
+### ~button /js/variables
+NEXT: Variable Declarations
+### ~