converting introductory documentation to README.md

Primarily for the purpose of having an easier starting-point for
documentation as this project is displayed on github.

Also, added a prominent note to use cl-interpol to help maximize
values of "perl compatible".

README.md

@@ -0,0 +1,30 @@
+# CL-PPCRE - Portable Perl-compatible regular expressions for Common Lisp
+
+## Abstract
+
+CL-PPCRE is a portable regular expression library for Common Lisp
+which has the following features:
+
+* It is **compatible with Perl** (especially when used in conjunction
+  with [cl-interpol](http://weitz.de/cl-interpol/), to allow
+  compatible parsing of regexp strings).
+* It is pretty **fast**.
+* It is **portable** between ANSI-compliant Common Lisp
+  implementations.
+* It is **thread-safe**.
+* In addition to specifying regular expressions as strings like in
+  Perl you can also use **S-expressions**.
+* It comes with a
+  **[BSD-style license](http://www.opensource.org/licenses/bsd-license.php)**
+  so you can basically do with it whatever you want.
+
+CL-PPCRE has been used successfully in various applications like
+[BioBike](http://nostoc.stanford.edu/Docs/),
+[clutu](http://clutu.com/),
+[LoGS](http://www.hpc.unm.edu/~download/LoGS/),
+[CafeSpot](http://cafespot.net/),
+[Eboy](http://www.eboy.com/), or
+[The Regex Coach](http://weitz.de/regex-coach/).
+
+Further documentation can be found in `doc/index.html`, or on
+[the cl-ppcre homepage](http://weitz.de/cl-ppcre/).