Add 'Binary' lesson to csintro. (#434)

docs/courses/csintro/binary.md

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+# Binary
+
+This lesson presents the concept of binary digits and base-2 notation.  Students will learn how data is stored digitally and how it can be read and accessed.
+
+## Lesson objectives
+
+Students will...
+* Understand what a bit and byte are and how they relate to computers and the way information is processed and stored.
+* Learn to count in Base-2 (binary) and translate numbers from Base-10 (decimal) to binary and decimal.
+* Apply the above knowledge and skills to create a unique program that uses binary counting as an integral part of the program.
+
+## Lesson structure
+
+* Introduction: Bits and Bytes
+* Unplugged Activity: Binary Vending Machine
+* Micro:bit Activity: Binary Transmogrifier
+* Project: Make a Binary Cash Register
+* Assessment: Rubric 
+* Standards: Listed
+
+## Lesson plan
+
+1. [**Overview**: Bits, bytes, binary](/courses/csintro/binary/overview)
+2. [**Unplugged**: Binary vending machine](/courses/csintro/binary/unplugged)
+3. [**Activity**: Binary transmogrifier](/courses/csintro/binary/activity)
+4. [**Project**: Make binary a cash register](/courses/csintro/binary/project)
+
+## Related standards
+
+[Targeted CSTA standards](/courses/csintro/binary/standards)