Improvements to the Introduction and Simple Patterns sections of intermediate/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.
Merge pull request #569 from ctjacobs/creating-lesson-on-regular-expressions

Improvements to intermediate/regex