Eigenvalue computation

[Azrael3000]

From an email:

 As the Eos is:
   p = \frac{rho_0 c0^2}{xi}*((\frac{\rho}{\rho_0})^xi-1), (xi=7, rho_0=1d3)
  so the matrix of \frac{\partial F}{\parial u} is
  {0                                      ,  1 }
  {-v^2+c0^2*(rho/rho0)^6,  2v}

  Finaly, the eigenvalue will be:
  v + sign*c0*(rho/rho0)^3

  So I don't understand why it is as following in your code.
  ev = 0.5d0*( 3d0*v(i) + sgn*sqrt( 5d0*v(i)**2 + 4d0*c0**2*(u(i,1)/1d3)**6 )  )

Bug or feature?

[Azrael3000]

Fixed in commit 7e2590.

Started to add documentation to avoid such bugs in the future.