fix bug in actionvalues alphavectorpolicy

[MaximeBouton]

The size of the returned array was not correct.

[coveralls]

Pull Request Test Coverage Report for Build 61

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.8%) to 88.379%

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Totals
Change from base Build 56:	0.8%
Covered Lines:	578
Relevant Lines:	654

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💛 - Coveralls

[zsunberg]

oh shoot! sorry I messed this up! Thanks for fixing it!

btw, in the future I think valuepairs that returns a list of action-value pairs might be less error-prone #15