Performs a 1way ANOVA.
The onway ANOVA tests the null hypothesis that 2 or more groups have the same population mean. The test is applied to samples from two or more groups, possibly with differing sizes.
Parameters :  sample1, sample2, ... : array_like


Returns :  Fvalue : float
pvalue : float

Notes
The ANOVA test has important assumptions that must be satisfied in order for the associated pvalue to be valid.
If these assumptions are not true for a given set of data, it may still be possible to use the KruskalWallis Htest (`stats.kruskal`_) although with some loss of power
The algorithm is from Heiman[2], pp.3947.
References
[R48]  Lowry, Richard. “Concepts and Applications of Inferential Statistics”. Chapter 14. http://faculty.vassar.edu/lowry/ch14pt1.html 
[R49]  Heiman, G.W. Research Methods in Statistics. 2002. 