Couple regex doc clarifications.

Closes #21.

README.md

@@ -88,6 +88,10 @@ repren -p patfile --word-breaks --full mydir1
 
 # Same as above, for all case variants:
 repren -p patfile --word-breaks --preserve-case --full mydir1
+
+# Same as above but including only .py files and excluding the tests directory
+# and any files or directories starting with test_:
+repren -p patfile --word-breaks --preserve-case --full --include='.*[.]py$' --exclude='tests|test_.*' mydir1
 ```
 
 ## Usage
@@ -122,15 +126,15 @@ scripts that would scare your mother.
 
 No dependencies except Python 3.10+. It's easiest to install with pip:
 
-```
+```bash
 pip install repren
 ```
 
 Or, since it's just one file, you can copy the
 [repren.py](https://raw.githubusercontent.com/jlevy/repren/master/repren/repren.py) script
 somewhere convenient and make it executable.
 
-## Try it
+## Try It
 
 Let's try a simple replacement in my working directory (which has a few random source
 files):

devtools/generate_readme.py

@@ -1,3 +1,5 @@
+#!/usr/bin/env python
+
 from jinja2 import Template
 import os
 import sys

repren/repren.py

@@ -201,6 +201,9 @@
 
 ## Notes
 
+- All pattern matching is via standard
+  [Python regular expressions](https://docs.python.org/3/library/re.html).
+
 - As with sed, replacements are made line by line by default.
   Memory permitting, replacements may be done on entire files using `--at-once`.
 
@@ -847,7 +850,7 @@ def main() -> None:
     parser.add_argument(
         "--walk-only",
         help=(
-            "like --dry-run, but only walk and list that will be processed "
+            "like --dry-run, but only walk directories and list files that will be processed "
             "(good for confirming your --include and --exclude patterns)"
         ),
         dest="walk_only",
@@ -989,6 +992,11 @@ def format_flags(flags: int) -> str:
     main()
 
 # TODO:
-#   --undo mode to revert a previous run by using .orig files; --clean mode to remove .orig files
+#   consider using regex for better Unicode support (but only gracefully, such as
+#     with a dynamic import, if those features like Unicode character properties are needed)
+#   --undo mode to revert a previous run by using .orig files
+#   --clean mode to remove .orig files
+#   --orig_suffix to allow for backups besides .orig, including for these use cases
 #   Log collisions
 #   Separate patterns file for renames and replacements
+#   Should --at-once be the default?