Include a file tracking the known issues

ISSUES.md

+## A list of known (and hopefully soon solved) issues of ELPA ##
+
+For more details and recent updates please visit the online [issue system] (https://gitlab.mpcdf.mpg.de/elpa/elpa/issues)
+
+### ELPA 2016.05.002 release  ###
+
+- QR decomposition fails for certain combinations of matrix sizes, number of eigenvalues to compute and block size
+
+### ELPA 2016.05.001 release  ###
+
+- QR decomposition fails for certain combinations of matrix sizes, number of eigenvalues to compute and block size
+- The generated check-scripts (in the step "make check") do not call the binary with "mpiexec" when ELPA is build with
+  MPI
+