Add missing command "git" in README

README.asciidoc

@@ -49,7 +49,7 @@ Generate bar chart with commits by year:
 $ python gitchart.py -r /path/to/gitrepo/ commits_year commits_year.svg
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-Generate bar chart with commits by version (tag):
+Generate bar chart with commits by version (git tag):
 ----
 $ cd /path/to/gitrepo/