MINOR: add header to _evalTFP.py
DOC: write documentation for evalMixedTF
DOC: minor changes
DOC: minor changes
DOC: fix sum symbol
TEST: move tests form mod1() to the new location
TEST: move tests for mod2() to the new location.
BUGFIX: add support for all LTI structures.
Merge branch 'master' of https://github.com/ggventurini/python-deltasigma into tests

Conflicts:
	deltasigma/_mod1.py
	deltasigma/_mod2.py
TEST: add tests for l1norm()