environment: add gurobipy (#127)

* environment: add gurobipy

* environment: add gurobi channel

environment.yaml

@@ -3,6 +3,7 @@ channels:
   - defaults
   - conda-forge
   - bioconda
+  - http://conda.anaconda.org/gurobi
 dependencies:
   - python
   - pip
@@ -44,6 +45,9 @@ dependencies:
   - shapely
   - libgdal
 
+  # Solvers
+  - gurobi:gurobi # until https://github.com/conda-forge/pypsa-feedstock/issues/4 closed
+
   - pip:
     - git+https://github.com/FRESNA/vresutils.git#egg=vresutils
     - git+https://github.com/PyPSA/glaes.git#egg=glaes