Update README installation instructions

... after removing mamba from the Bioconda recipe, installation
instructions should explicitely state that it is required for cluster
mode.

Also: Now using the most recent R version for pinning (R 4.0.3 is marked
broken in anaconda).

README.md

@@ -13,22 +13,18 @@ To run `wg-blimp` you need a UNIX environment that contains a [Bioconda](http://
 It is advised to install `wg-blimp` through Bioconda. It is **strongly** recommended to install `wg-blimp` in a fresh environment, as it has many dependencies that may conflict with other packages, for this you can use:
 
 ```
-conda create -n wg-blimp wg-blimp r-base==4.0.3
+conda create -n wg-blimp wg-blimp r-base==4.1.1
 ```
 
-***WARNING***: Installing wg-blimp will install mamba and conda as a dependency, so make sure to not install `wg-blimp` in an environment that is used for other purposes, and always run `conda deactivate` after running `wg-blimp`.Otherwise you might accidentally use the `conda` version installed by `wg-blimp` instead of your own.
+***WARNING***: You need to install `mamba` as well if you intend to use `wg-blimp`'s cluster mode (e.g. on SLURM clusters) using the following command:
 
-### Docker
-
-We bundled a full `wg-blimp` installation into a Docker container. You may pull our image using
 ```
-docker pull imimarw/wg-blimp:v0.9.8
+conda create -n wg-blimp wg-blimp r-base==4.1.1 mamba
 ```
 
-Once the image was downloaded and extracted, you can start the docker container with
-```
-docker run -it -v <directory-to-be-mounted>:<mounted-directory-in-container> imimarw/wg-blimp:v0.9.8
-```
+However, this will install `mamba` and `conda` as a dependency, so make sure to not install `wg-blimp` in an environment that is used for other purposes, and always run `conda deactivate` after running `wg-blimp`.
+Otherwise you might accidentally use the `conda` version installed along `mamba` instead of your own.
+
 
 ### From source
 You can also install `wg-blimp` from source using