DOC: added section about disabling spell checking

Describe the 'spell-check-disable' and 'spell-check-enable'

Also added slash before all single quotes.  This bug was messing
up pandoc's formatting.

Author: dave3d

README.md

@@ -11,36 +11,66 @@ Here is how it is typically run:
 
     python comment_spell_check.py --exclude Ancillary $SIMPLEITK_SOURCE_DIR/Code
 
-This command will recursively find all the '.h' files in a directory,
+This command will recursively find all the \'.h\' files in a directory,
 extract the C/C++ comments from the code, and run a spell checker on them.
-The **'--exclude'** flag tells the script to ignore any file that has
-'Ancillary' in its full path name.  This flag will accept any
+The **\'\-\-exclude\'** flag tells the script to ignore any file that has
+\'Ancillary\' in its full path name.  This flag will accept any
 regular expression.
 
-In addition to pyenchant's English dictionary, we use the words in
+In addition to pyenchant\'s English dictionary, we use the words in
 **additional_dictionary.txt**.  These words are proper names and
 technical terms harvest by hand from the SimpleITK and ITK code bases.
 
 If a word is not found in the dictionaries, we try two additional checks.
 
 1. If the word starts with some known prefix, the prefix is removed
-...and the remaining word is checked against the dictionary.  The prefixes
-...used by default are **'sitk'**, **'itk'**, and **'vtk'**.  Additional
-...prefixes can be specified with the **'--prefix'** command line argument.
+   and the remaining word is checked against the dictionary.  The prefixes
+   used by default are **\'sitk\'**, **\'itk\'**, and **\'vtk\'**.  Additional
+   prefixes can be specified with the **\'\-\-prefix\'** command line argument.
 
 2. We attempt to split the word by capitalization and check each
-...sub-word against the dictionary.  This method is an attempt to detect
-...camel-case words such as 'GetArrayFromImage', which would get split into
-...'Get', 'Array', 'From', and 'Image'.  Camel-case words are very commonly
-...used for code elements.
+   sub\-word against the dictionary.  This method is an attempt to detect
+   camel-case words such as \'GetArrayFromImage\', which would get split into
+   \'Get\', \'Array\', \'From\', and \'Image\'.  Camel-case words are very commonly
+   used for code elements.
 
-The script can also process other file types.  With the **'--suffix'**
+The script can also process other file types.  With the **\'\-\-suffix\'**
 option, the following file types are available: Python (.py), C/C++
 (.c/.cxx), CSharp (.cs), Text (.txt), reStructuredText(.rst), Markdown (.md),
 Ruby (.ruby), R (.R), and Java (.java).  Note that reStructuredText files are
 treated as standard text.  Consequentially, all markup keywords that are not
 actual words will need to be added to the additional/exception dictionary.
 
+## Disabling Spell Checking
+
+Spell checking can be disabled for sections of code by using special
+
+comments.  The following comments will disable spell checking until
+the corresponding end comment is found.
+```
+// spell-check-disable
+
+// This comment will not be spell checked.
+
+// spell-check-enable
+```
+
+Note that for C-style, multi-line comments, the disable and enable
+comments must be in seperate comments.  If the disable command
+is found in a multi-line comment, spell checking will be
+disabled for the entire multi-line comment.
+
+```
+/*
+spell-check-disable
+spell-check-enable
+This comment will NOT be spell checked
+*/
+/* spell-check-enable */
+/* This comment WILL be spell checked */
+```
+
+
 ## Dictionary notes
 
 We use [PySpellChecker](https://github.com/barrust/pyspellchecker) as the