Add predict_mixture() to predict the effects of a mixture of two toxicants.

Closes #23.

See merge request !16

Fix documentation of ecxsys and predict_ecxsys

See merge request !17

as it is no longer recommended since testhat version 2.1.0

update merge request template and readme

See merge request !15

Major rework of the source code and documentation. Refactor everything to improve usability and to make debugging and extending the package easier.

See merge request !3

Major rework of the source code and documentation. Refactor everything to improve usability and to make debugging and extending the package easier. See NEWS.md for details.

Last changes for first public version. Closes #11.

See merge request !12

Bugfix/warnings

Closes #15

See merge request !11

Fix failing test under devtools::check()

I ran the `testthat` tests but forgot to run `devtools::check()`. Somehow the options are handled differently in both cases.

See merge request !7

Remove BugReports url from DESCRIPTION

See merge request !6

because non-emplyees can't open isses.

Prevent ecxsys from modifying options, closes #10

Closes #10

See merge request !5

Reset them every time drm is called or when ecxsys sets show.error.messages to FALSE.

improve documentation of all user-facing functions

Closes #2

See merge request !4

Update README.md

See merge request !1