update README

Author: AlessioDelConte

README.md

@@ -319,14 +319,14 @@ The plugin can be tested with the following example:
       selected structure on a web server using the APIs.
 5. Once the results are ready they will be parsed and visualized on the structure in the PyMOL interface.
 
-<p style="text-align:center">
+<p align="center">
     <img height="400" src="doc_imgs/edges.png" width="650"/>
 </p>
 
 6. Now the edges can be filtered based on the type of interaction, frequency, and all the various tools can be used.
    E.g. we can see the `probabilistic interchain residue contact map` of the $\pi-\pi$ stack interactions:
 
-   <p style="text-align:center">
+   <p align="center">
        <img height="400" src="doc_imgs/contact_map.png" width="650"/>
    </p>
 
@@ -336,6 +336,6 @@ The plugin can be tested with the following example:
    automatically. One example is the following, were we set a RMSD cut value of 3.5 $\AA$, yielding 5 different
    clusters:
 
-   <p style="text-align:center">
+   <p align="center">
        <img height="400" src="doc_imgs/clusters.png" width="650"/>
    </p>