Wrong paths to source files of examples on current master branch

[JMairhofer]

In some of the README files describing the use of the simple examples (twoTank etc.) the paths to the source files are not correct. Probably because folders were moved and renamed without updating the README.

In the README of the multicomponent diffusion example:
fuller = "../models/fullerEtAlDiffusion/src"
has to be replaced by
fuller = "./src"

In the README of the twoTanks example:
flowrate ="../models/flowrate/src"
twoTank="../models/twoTank/src"

should be

flowrate ="../MoDeNaModels/flowrate/src"
twoTank="../MoDeNaModels/twoTank/src"