Change git clone links to gitlab.

docs/installation.md

 # Installation
 Clone this repository and install COMBO (we suggest using virtualenv/conda with Python 3.6+):
 ```bash
-git clone https://github.com/ipipan/combo.git
+git clone https://gitlab.clarin-pl.eu/syntactic-tools/clarinbiz/combo.git
 cd combo
 python setup.py develop
 combo --helpfull