Improve README.md Installation section (soxoj#690)

Clone and install manually is duplicated in 2 places and can be merged.

Author: PeterDaveHello

README.md

@@ -57,17 +57,14 @@ Also you can run Maigret using cloud shells and Jupyter notebooks (see buttons b
 # install from pypi
 pip3 install maigret
 
-# or clone and install manually
-git clone https://github.com/soxoj/maigret && cd maigret
-pip3 install .
-
 # usage
 maigret username
 ```
 
 ### Cloning a repository
 
 ```bash
+# or clone and install manually
 git clone https://github.com/soxoj/maigret && cd maigret
 pip3 install -r requirements.txt