scripts: Added <^> to punescape

Mainly for ^ for centering:

  "%{hi!%}^8s"        -> "  hi!   "

Note we can right bias with the nested modifier!

  "%{%{hi!%}^7s%}>8s" -> "   hi!  "

Also note this does _not_ support fill characters like python's format.
I'm not sure it's tractable with %-modifiers, python's format must get
up to some funky parsing to make this work ("%s<s"?).

I think this also fixed the behavior of left-aligning numbers? Seems we
weren't handling that before.

scripts/treemapsvg.py

@@ -428,10 +428,10 @@ def punescape(s, attrs=None, start=None, end=None, submatch=None):
                 '|' 'u....'
                 '|' 'U........'
                 '|' '\((?P<field>[^)]*)\)'
-                    '(?P<format>[+\- #0-9\.]*[siIdboxXfFeEgG])'
+                    '(?P<format>[<^>+\- #0-9\.]*[siIdboxXfFeEgG])'
                 '|' '\{'
                 '|' '\}'
-                    '(?P<subformat>[+\- #0-9\.]*[siIdboxXfFeEgG])' ')')
+                    '(?P<subformat>[<^>+\- #0-9\.]*[siIdboxXfFeEgG])' ')')
 
     def format(f, v):
         if f[-1] in 'dboxX':
@@ -447,10 +447,14 @@ def punescape(s, attrs=None, start=None, end=None, submatch=None):
                 f = f.replace('i', 's').replace('I', 's')
                 if '+' in f and not v.startswith('-'):
                     v = '+'+v
-                f = f.replace('+', '').replace('-', '')
+                f = f.replace('+', '')
         else:
-            f = ('<' if '-' in f else '>') + f.replace('-', '')
             v = str(v)
+
+        if '-' in f:
+            f = '<' + f.replace('-', '')
+        elif not any(d in f for d in '<^>'):
+            f = '>' + f
         # note we need Python's new format syntax for binary
         return ('{:%s}' % f).format(v)