IMF IS CORRECTLY FIT WITH SIMULATED DATA

Two important changes are implemented within modules in
myanalysis.py.

1) simulate_cmd
   ============

   - Line defining yrantmparr had a MAJOR bug.
   - Bug: yrantmparr took samples with ymin=min(dN/dM*delM)
     and ymax=max(dN/dM*delM) over the range of masses
     mass_min_global and mass_max_global. The error is
     that the number of samples created for masses near where
     dN/dM is a minimum *always* --> 0. Thus for any power
     law with alpha_in>0, the data sample ended up having
     alpha >> alpha_in.
   - Two hints were useful in finding the bug:
     a) set testing == 1 within simulate_cmd, and alpha=0.05.
        Expected many samples between 0 and an almost constant
        dN/dM max, instead got only a sliver of data between
        dN/dM min and dN/dM max.
     b) For very high alpha, the fits always seemed almost
        adequate, thus for alpha_in=5, alpha_out ~ 5+, but alpha_in=2,
        alpha_out ~ 5+. This is because high alpha power-law IMFs
        will by construction have very few stars near dN/dM min.
   - Simple fix: yrantmparr now set to produce samples between
     0 <= y < 1.02 * (dN/dM*delM)   *recall that f_Salpeter and
     f_chabrier output dN/dM multiplied by the (usually non-constant)
     spacing in dM [ note, currently, read_iso_darth does have a
     constant spacing in mass, unless interpolate=False...see two
     commits before ].

2)  f_salpeter, f_chabrier
    ======================

    - f_chabrier: in analogy with f_salpeter, dN_arr is *NOT* set
      to zero outside of mass_min and mass_max. Instead it is only
      normalized to integrate to 1 within mass_min and mass_max. It
      is only set to zero for M > 0.1 Msun and M > 100 Msun (if those
      values are present in the input mass_arr).

    - f_salpeter: dN_arr was set to zero within mass_arr < mass_min and
      mass_arr > mass_max if kwargs['normalize'] == False. This has
      been deleted.

3)  estimate_required_n:
    ===================

    - program calculates ratio of desired number of stars in observed
      magnitude range f_cut, vs number of stars obtained integrated over
      mass_min_global < M < mass_max_global, f_all.
    - Recall that for MC sampling, we construct a box with ymin = 0
      and ymax = max(dN/dM * delM). Thus, the number of stars that
      should be generated should be even higher than f_all.
    - Thus simulate_cmd currently generates 10*f_all stars, but might
      crash in case of very pathological IMFs with very high alpha,
      in these cases simply change 10*f_all to 50*f_all [not in
      estimate_required_n but in simulate_cmd]