Fix typos

doc/nimgrep.txt

@@ -25,9 +25,9 @@ Compile nimgrep with the command::
 And copy the executable somewhere in your ``$PATH``.
 
 
-Command line switches
-=====================
-
+Command line switches
+=====================
+
 Usage:
   nimgrep [options] [pattern] [replacement] (file/directory)*
 Options:
@@ -37,7 +37,7 @@ Options:
   --re                pattern is a regular expression (default); extended 
                       syntax for the regular expression is always turned on
   --recursive         process directories recursively
-  --confirm           confirm each occurence/replacement; there is a chance 
+  --confirm           confirm each occurrence/replacement; there is a chance 
                       to abort any time without touching the file
   --stdin             read pattern from stdin (to avoid the shell's confusing
                       quoting rules)