Fixed VCS relative paths

Relative paths should be relative to the current directory, not
relative to the root of the working copy. Also, ‘-r’ was added to the
Git remove command to allow directory recursion.

Fixes #163
Update CHANGES
Exclude openpyxl==2.1.0 as a dependency

openpyxl==2.1.0 broke tests (see #161). In openpyxl==2.1.1 these tests
are no longer broken so the old dependency requirements were restored
with an exclusion of the broken version.

Fixes #161
Bump release version number
Merge branch 'hotfix/v0.8.3'