Fix readme reference

See merge request AlekSIS/official/AlekSIS-App-Chronos!222

Resolve "Names of subjects should not have to be unique"

Closes #158

See merge request AlekSIS/official/AlekSIS-App-Chronos!221

[Fixtures] Fix number and period of validity ranges

See merge request AlekSIS/official/AlekSIS-App-Chronos!220

Remove admin user from test data

See merge request AlekSIS/official/AlekSIS-App-Chronos!219

Add trademark hint to readme

See merge request AlekSIS/official/AlekSIS-App-Chronos!218

Resolve "Allow editing of subject field on Group model in frontend"

Closes #156

See merge request AlekSIS/official/AlekSIS-App-Chronos!215

Resolve "Announcements are not shown on substitutions printout"

Closes #157

See merge request AlekSIS/official/AlekSIS-App-Chronos!216

Update dev dependencies and reformat

See merge request !217

Merge branch '155-automaticplan-doesn-t-look-at-versions-between-the-last-revision-and-the-current-revision' into 'master'

Resolve "AutomaticPlan doesn't look at versions between the last revision and the current revision"

Closes #155

See merge request AlekSIS/official/AlekSIS-App-Chronos!214

Add makemessages env to tox.ini

See merge request AlekSIS/official/AlekSIS-App-Chronos!213

Merge branch '154-nameerror-at-app-resint-live_documents-pdf-name-timedelta-is-not-defined' into 'master'

Resolve "NameError at /app/resint/live_documents/*.pdf: name 'timedelta' is not defined"

Closes #154

See merge request AlekSIS/official/AlekSIS-App-Chronos!212

Bump version to 2.1.dev0

See merge request AlekSIS/official/AlekSIS-App-Chronos!211

Resolve "Automatically create a PDF file of the substitution plan"

Closes #116

See merge request AlekSIS/official/AlekSIS-App-Chronos!191

Resolve "Events replace lessons"

Closes #127

See merge request AlekSIS/official/AlekSIS-App-Chronos!207

Update changelog from 2.0

See merge request AlekSIS/official/AlekSIS-App-Chronos!210

(cherry picked from commit 3dd7f9f3)