Fix bugs

1. Species with less than five individuals were originally excluded from
both iISD and size-abundance relationship. However, the exclusion is
only necessary for the former.
2. Change species range in plot_obs_pred so that R**2 is visible.
3. Fix (a lot of) typos in plot_four_patterns_single_ver2.
4.Change bin size in Fig. 1 to be consistent with the rest of the
analyses.