tweak wording to msprime paper

Author: petrelharp

_resources/kelleher2016.md

@@ -3,12 +3,13 @@ type: paper
 doi: 10.1371/journal.pcbi.1004842
 timestamp: 2016-04-04
 ---
-This is where it all started. Here we introduce the
+This is where the tree sequence data structure
+was first described. Here we introduce the
 [msprime](/software/msprime.html) coalescent simulator and
 the core algorithms and data structures that would later
 be separated out into [tskit](software/tskit.html).
 Read this paper if you would like to find out more about
 coalescent simulation, or to understand the core tree sequence
 algorithms and theoretical results. _Note:_ much
 of the terminology has been updated since this original publication
-as the models were generalised.
+as the models were generalised.