adding the 3 and 5 bin frequency results and updating the readme

results/agnosticPosterior/readme.md

-This directory includes three posterior files from the agnostic model analysis. 
-The analysis was run three times and the posteriors were combined to produce 
+This directory includes results for the agnostic model. Three analyses were 
+performed using different numbers of frequency bins from the PTA analysis.
+The results are included in directories: nFreq3, nFreq5, and nFreq9 for 
+analyses using 3, 5, and 9 frequency bins respectively. 
+
+Note that the 9 frequency bin results were used as final results in the 
+EPTA paper. 
+
+Within each analysis directory there are three posterior files - the 
+analysis was run three times and the posteriors were combined to produce 
 the paper figures. 
 
 This is the data behind the plot for Figure A2 in the EPTA DR2 paper IV