Clean up description of Tools/scripts/run_tests.py.

Also, add an entry for the script in Tools/scripts/README.

Tools/scripts/README

@@ -15,7 +15,7 @@ db2pickle.py            Dump a database file to a pickle
 diff.py                 Print file diffs in context, unified, or ndiff formats
 dutree.py               Format du(1) output as a tree sorted by size
 eptags.py               Create Emacs TAGS file for Python modules
-find_recursionlimit.py  Find the maximum recursion limit on this machine 
+find_recursionlimit.py  Find the maximum recursion limit on this machine
 finddiv.py              A grep-like tool that looks for division operators
 findlinksto.py          Recursively find symbolic links to a given path prefix
 findnocoding.py         Find source files which need an encoding declaration
@@ -53,6 +53,7 @@ redemo.py               Basic regular expression demonstration facility
 reindent.py             Change .py files to use 4-space indents
 reindent-rst.py         Fix-up reStructuredText file whitespace
 rgrep.py                Reverse grep through a file (useful for big logfiles)
+run_tests.py            Run the test suite with more sensible default options
 serve.py                Small wsgiref-based web server, used in make serve in Doc
 suff.py                 Sort a list of files by suffix
 svneol.py               Set svn:eol-style on all files in directory

Tools/scripts/run_tests.py

 """Run Python's test suite in a fast, rigorous way.
 
-The defaults are meant to be thorough but to skip certain resources are not
-used (by default) which can consume a lot of time and resources (e.g.,
-largefile) or can be distracting (e.g., audio and gui). These defaults
-can be overridden by simply passing a -u option to this script.
+The defaults are meant to be reasonably thorough, while skipping certain
+tests that can be time-consuming or resource-intensive (e.g. largefile),
+or distracting (e.g. audio and gui). These defaults can be overridden by
+simply passing a -u option to this script.
 
 """