Gentle formatting fixes we can run more often. (#443)

Fixes a bunch of inadvertently preformatted text due to >4 spaces after a bullet.

admin/reformat-aggressive.sh

@@ -1,6 +1,8 @@
 #!/bin/bash
 
 # Put main main Markdown files into canonical syntax (in place!) with markdownfmt.
+# XXX This is aggressive so we haven't been running. See also 
+# https://github.com/shurcooL/markdownfmt/issues?utf8=%E2%9C%93&q=is%3Aopen%20author%3Ajlevy%20
 
 set -e -u -o pipefail
 

admin/reformat-gentle.sh

@@ -0,0 +1,16 @@
+#!/bin/bash
+
+# Gently fix common Markdown formatting errors. Should be minimally invasive.
+
+set -e -u -o pipefail
+
+hash repren >/dev/null 2>&1 || {
+  echo >&2 "repren missing: Install https://github.com/jlevy/repren and re-run"
+  exit 1
+}
+
+cd $(dirname $0)/..
+
+# Extra spaces following a bullet replaced by tab per mkdownfmt convention.
+# Leave other stuff alone.
+repren --from '^(\s*)([-*])(\s*  +\s*)' --to '\1\2\t' README.md CONTRIBUTING.md