Merge pull request Qiskit#628 from diego-plan9/stable-0.5.6

Stable 0.5.6

Merge pull request Qiskit#617 from atilag/stable-0.5.5

Stable 0.5.5

Merge pull request Qiskit#559 from atilag/stable-0.5.4

Stable 0.5.4

Merge pull request Qiskit#517 from atilag/stable-0.5.3

Stable 0.5.3

Merge pull request Qiskit#488 from atilag/stable-0.5.2

Stable 0.5.2

Merge pull request Qiskit#470 from atilag/stable-0.5.1

pip release: 0.5.1

pip release: 0.5.0

pip release: 0.4.15 (Qiskit#454)

pip release: 0.4.15
* Fixed a bug with legacy code affecting Developer Challenge
* Disabled util_tests temporarily

pip release: 0.4.14

pip release: 0.4.13