Added a context manager to change directories and change back when the context exits. So you can go "with cd(dir): ..." and it will always come back to the directory that you were originally in.
Added a way to specify that certain source files should not be considered for inclusion into a library/executable.
Fixed an issue where if you specified command-line targets that depended on targets that were not yet defined (ie would be defined in a later build cycle), the auto targets would not be built. This is an issue because the later build cycle (may) depend on the auto targets.
Updated link module.