rms_test
  rms evaluates the root-mean-square norm of a vector or matrix

  X:
     1     2     3     4     5     6     7     8     9    10

  rms(x)
    6.2048


  A:
     5     4     3     2     1
     4     4     3     2     1
     0     3     3     2     1
     0     0     2     2     1

  rms(A):
    3.2016    3.2016    2.7839    2.0000    1.0000