put a short description and a roadmap draft

README.md

-HeLaz (2020)
+Hermite-Laguerre Z-pinch solver (2020)
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+
+Goal : Write the MOLI solver in Fortran and include a non linear Poisson bracket term to it.
+
+Roadmap :
+0) Write MOLI matlab solver in Fortran using Monli1D as starting point
+	0.1) go from 1D space to 2D fourier and from Hermite basis to Hermite-Laguerre basis <- current stage
+	0.2) implement linear Poisson equation in fourier space
+	0.3) implement moment hierarchy linear terms
+	0.4) implement explicit RK4 time solver
+	0.5) Benchmark with MOLI matlab results for Z-pinch
+
+1) Implementation of the non linear Poisson brackets term