add support for negative filters (-F field!=regex)

tablizer.pod

@@ -16,7 +16,7 @@ tablizer - Manipulate tabular output of other programs
       -s, --separator string            Custom field separator
       -k, --sort-by int|name            Sort by column (default: 1)
       -z, --fuzzy                       Use fuzzy search [experimental]
-      -F, --filter field=reg            Filter given field with regex, can be used multiple times
+      -F, --filter field[!]=reg         Filter given field with regex, can be used multiple times
       -T, --transpose-columns string    Transpose the speficied columns (separated by ,)
       -R, --regex-transposer /from/to/  Apply /search/replace/ regexp to fields given in -T
 
@@ -194,6 +194,10 @@ Fieldnames (== columns headers) are case insensitive.
 If you specify more than one filter, both filters have to match (AND
 operation).
 
+These field filters can also be negated:
+
+    fieldname!=regexp
+
 If the option B<-v> is specified, the filtering is inverted.