Commit lzw, compress, uncompress

Solution to Problem #3 by Daniel Hartwig

* code/compress: new file
* code/uncompress: new file
* code/lzw.scm: new file
Add Problem #7, Animated GIF

* ch02_web1.texi: add Problem #7
* g100.texi: update index
Include compress scripts into the main doc

* ch01_bin.texi: modified
Merge branch 'master' of https://github.com/spk121/guile100