Issue #144: update docs about byexample.regex instead of re

The commit was originally developmented for #128
(cherry picked from commit a3ebe9b)

docs/contrib/how-to-define-new-zones-where-to-find-examples.md

@@ -42,7 +42,7 @@ everything except the code between ``<pre>`` and ``</pre>`` tags.
 This is what you need to write:
 
 ```python
->>> import re
+>>> import byexample.regex as re
 >>> from byexample.finder import ZoneDelimiter
 
 >>> class HTMLPreBlockDelimiter(ZoneDelimiter):
@@ -64,6 +64,11 @@ or set of several extensions.
 The ``zone_regex`` method should return a regular expression to find and capture
 the zones.
 
+While you can use the standard
+[``re`` module](https://docs.python.org/3/library/re.html) it is
+recommended to use ``byexample.regex`` which has some built-in
+optimizations.
+
 And optionally, the ``get_zone`` can be overridden to post-process the captured
 string: use it to remove any spurious string that may had been captured.
 

docs/contrib/how-to-support-new-finders-and-languages.md

@@ -60,7 +60,7 @@ To accomplish this we need to create a regular expression to find the
 ``~~~``, where the snippet of code is and where the expected output is.
 
 ```python
->>> import re
+>>> import byexample.regex as re
 
 >>> example_re = re.compile(r'''
 ...     # begin with ~~~
@@ -107,6 +107,11 @@ The ``indent`` group is to count how many spaces are not part of the example
 and they are just for indentation: ``byexample`` will *drop* the first line that
 has a lower level of indentation and any subsequent line.
 
+While you can use the standard
+[``re`` module](https://docs.python.org/3/library/re.html) it is
+recommended to use ``byexample.regex`` which has some built-in
+optimizations.
+
 ### Detect the language
 
 Then, the finder needs to determinate in which language the example
@@ -351,7 +356,7 @@ you do not need to install a real ``ArnoldC`` compiler.
 ...     output = []
 ...     for line in source_code.split('\n'):
 ...         if line.startswith("TALK TO THE HAND"):
-...             to_print = re.search(r'"([^"]*)"', line).group(1)
+...             to_print = re.compile(r'"([^"]*)"').search(line).group(1)
 ...             output.append(to_print + '\n')
 ...
 ...     return '\n'.join(output)