metadata read fix in ponysay-tool + fix documentation on metadata

Signed-off-by: Mattias Andrée <maandree@operamail.com>

manuals/ponysay.texinfo

@@ -2379,11 +2379,15 @@ begins with a line with exactly 3 dollar signs and nothing else (@code{$$$}), an
 end in the same way direct follow by the pony image starting from the next line.
 
 A metadata tag consists of a tag name in upper case and a tag value, with a colon
-(@code{:}), optionally with regular spaces or tab spaces. Multiple tag names can
+(@code{:}), optionally with surrounding regular spaces or tab spaces, but at least
-be used multiple times or can be completely skipped. There are only a few tags,
+one regular space or tab space directly after the colon. The name can only consist
-namely @var{BALLOON TOP}, @var{BALLOON BOTTOM}, @var{MASTER}, @var{FREE}, that
+of A to Z (upper case ASCII letters) and regular spaces. All tab spaces in the tag
-absolutely should not be used muliple tag; a general rule is that a tag desribing
+names and values are handled as regular spaces. Multiple tag names can be used
-a pony should be duplicated exactly as many times as there are ponies in the image.
+multiple times or can be completely skipped. There are only a few tags, namely
+@var{BALLOON TOP}, @var{BALLOON BOTTOM}, @var{MASTER} and @var{FREE}, that absolutely
+should not be used muliple tag, but nor should @var{WIDTH} and @var{HEIGHT}; a
+general rule is that a tag desribing a pony should be duplicated exactly as many
+times as there are ponies in the image.
 
 Any line that does not conform to the format of a tag line is a part of the comment
 field. Leading line breaks in the comment field is ignored.

src/ponysaytool.py

@@ -702,7 +702,7 @@ class PonysayTool():
         data = {}
         comment = []
         for line in meta:
-            if ': ' in line:
+            if ': ' in line.replace('\t', ' '):
                 key = line.replace('\t', ' ')
                 key = key[:key.find(': ')]
                 test = key