Improvements to the Introduction and Simple Patterns sections of inte…

…rmediate/regex.

Main changes:
- Fixed the links to other sections and the Glossary.
- Added files containing the 'evil' data to data/evil.
- Created some exercises for the Simple Patterns section.
- Corrected a few typos and made some paragraphs clearer.
- Split up the Simple Patterns section into subsections.
- Added the intermediate/regex section to the Makefile.
- Added an index page.

Makefile

@@ -66,6 +66,7 @@ MOST_SRC = \
 # All source pages (including things not in the book).
 ALL_SRC = \
 	contents.md \
+        $(wildcard intermediate/regex/*.md) \
 	$(wildcard intermediate/python/*.md) \
 	$(wildcard intermediate/doit/*.md) \
 	$(wildcard slides/*.html) \

data/evil/notebook-1.txt

@@ -0,0 +1,12 @@
+Site	Date		Evil (milliVaders)
+Baker 1	2009-11-17	1223.0
+Baker 1	2010-06-24	1122.7
+Baker 2	2009-07-24	2819.0
+Baker 2	2010-08-25	2971.6
+Baker 1	2011-01-05	1410.0
+Baker 2	2010-09-04	4671.6
+Baker 2	2012-02-25	1099.0
+Baker 1	2013-01-01	950.9
+Baker 1	2012-07-23	2000.0
+Baker 2	2013-08-22	3500.4
+Baker 2	2014-01-02	4510.1

data/evil/notebook-2.txt

@@ -0,0 +1,12 @@
+Site/Date/Evil
+Davison/May 23, 2010/1724.7
+Pertwee/May 24, 2010/2103.8
+Davison/June 19, 2010/1731.9
+Davison/July 6, 2010/2010.7
+Pertwee/Aug 4, 2010/1731.3
+Pertwee/Sept 3, 2010/4981.0
+Pertwee/June 20, 2011/2103.8
+Davison/June 5, 2011/1731.9
+Davison/Dec 14, 2011/2200.4
+Pertwee/Nov 2, 2011/930.1
+Pertwee/Sept 5, 2011/5000.9

intermediate/regex/01-intro-regex.md

@@ -7,17 +7,16 @@ title: Introduction to Regular Expressions
 A couple of years after the Death Star exploded, a hot-shot reporter at
 the Daily Planet heard that children in the Shire were starting to act
 strangely. Our supervisor sent some grad students off to find out what
-was going on. Things didn't go so well for them, but their notebooks
-were recovered and later transcribed.
+was going on. Every student's notebook containing measurements of background evil levels (in milliVaders)
+at various locations in the Shire was later transcribed and stored as a data file.
 
-Our job is to read 20 or 30 files, each of which contains several
+Our job is to read 20 or 30 of these data files, each of which contains several
 hundred measurements of background evil levels, and convert them into a
 uniform format for further processing. Each of the readings has the name
 of the site where the reading was taken, the date the reading was taken
-on, and of course the background evil level in millivaders. The problem
+on, and of course the background evil level in milliVaders. The problem
 is, these files are formatted in different ways. Here is the first one:
 
-
 ![image](img/01-intro-notebook-1.png) 
 
 A single tab character divides the fields in each row into columns. The
@@ -53,7 +52,7 @@ year-month-day.
 
 We could parse these files using basic string operations, but it would
 be difficult. A better approach is to use [regular
-expressions](glossary.html#regular-expression). A regular expression is
+expressions](../../gloss.html#regular-expression). A regular expression is
 just a pattern that can match a string. They are actually very common:
 when we say `*.txt` to a computer, we mean, "Match all of the filenames
 that end in `.txt`." The `*` is a regular expression: it matches any