Added link to hello world section and quantum emoticon (#55)
Added link to hello world section and quantum emoticon (#55)

* Fixed global phase of cu3. Added explanation of the equivalance of gates up to the global phase emphasizing CX (control not) is not equivalent to cu3(pi, 0, pi)

* Fixed issue #32

* Added a link to quantum emoticon from index page

antoniomezzacapo/qiskit-tutorial