Adding a changelog file

For the git tutorial. It contains my name and date.
Adding a line to main_file.txt

To build up a second commit.
Merge branch 'douglasjacobsen/cosim3/new-branch' into matthewhoffman/cosim2/new-branch

* douglasjacobsen/cosim3/new-branch:
  Adding a line to main_file.txt
  Adding a changelog file

Conflicts:
	Changelog