Adapt install.txt to achieve usage of pygame on debian6

but not yet working
Merge branch 'master' of https://github.com/nicolas-fricke/semmul2013-group1
Merge branch 'master' of https://github.com/nicolas-fricke/semmul2013-group1
Merge branch 'master' of https://github.com/nicolas-fricke/semmul2013-group1
Update install.txt, pygame done, but still problems
Merge branch 'master' of https://github.com/nicolas-fricke/semmul2013-group1
Merge branch 'master' of https://github.com/nicolas-fricke/semmul2013-group1
Add description of old semantic clustering
Merge branch 'master' of https://github.com/nicolas-fricke/semmul2013-group1