Update use_case.md

Changes to the wiki added to the use_case.md file
Created and added arguments to parse and defaults as specified in the wiki for CONCOCT
Nose skeleton and a small test data composition signature file
added output class, reading in composition and coverage, generate features for composition
Integration tests instead of long name
Renamed again, integration tests did not execute
Integration tests for checking exit status and that output dir is created
empty test data files
Removed big test data file
Restructured to CONCOCT script
Ignore adapted to new structure
Collect returncode correctly, test for nonzero error code finished
Fixed wrong argument name in argument parser
Random data to run tests on
Real clustering made in integration tests, failing output directory creation
Added tests for all output files creation
Tests for creation of unique output directory if given exists
init file for concoct module
pca and first Gaussian mixture, not finished
first version, need to test