NEP-PACK 0.2.8

New release:

• New method: contour block_SS #189
• Refactorization of the contour integral solvers: Introduction of MatrixIntegrator
• New tutorials:
  • Parallelization + contour: https://nep-pack.github.io/NonlinearEigenproblems.jl/tutorial_contour/,
  • Nanophotonics + gmsh: https://nep-pack.github.io/NonlinearEigenproblems.jl/tutorial_nano1/
  • Your own solver: https://nep-pack.github.io/NonlinearEigenproblems.jl/tutorial_newmethod/
  • Fluid mech: #194 https://nep-pack.github.io/NonlinearEigenproblems.jl/hydrotutorial/
• Support for chebyshev polys #190
• Moved from Arpack to ArnoldiMethod.jl to lessen fortran dependence #191