updated the documentation

Author: JLSteenwyk

docs/usage/index.rst

@@ -290,7 +290,7 @@ Compositional bias per site
 ###########################
 
 Function names: compositional_bias_per_site; comp_bias_per_site; cbps |br|
-Command line interface: pk_compositional_bias_per_site; pk_compositional_bias_per_site; pk_cbps
+Command line interface: pk_compositional_bias_per_site; pk_comp_bias_per_site; pk_cbps
 
 Calculates compositional bias per site in an alignment.
 
@@ -1337,9 +1337,9 @@ Calculate treeness statistic for a phylogeny.
 Higher treeness values are thought to be desirable because they
 represent a higher signal-to-noise ratio.
 
-Treeness describes the proportion of the tree distance found on
-internal branches. Treeness can be used as a measure of the 
-signal-to-noise ratio in a phylogeny. 
+Treeness is the sum of internal branch lengths divided by the total
+tree length. Therefore, values range from 0 to 1. Treeness can be
+used as a measure of the signal-to-noise ratio in a phylogeny. 
 
 Calculate treeness (also referred to as stemminess) following
 Lanyon, The Auk (1988), doi: 10.1093/auk/105.3.565 and