add documentation for metaphlan3 install

Closes #20 (closed)

metaphlan3/README.md

+# Metaphlan3 and StrainPhlan3
+
+## Install
+
+> You need to perform install from the head of submission (tars-0) since an internet connection is needed
+
+[Instructions here](https://github.com/biobakery/MetaPhlAn/wiki/MetaPhlAn-3.0#installation), in brief what has been done:
+
+```bash
+conda create --name mpa -c bioconda python=3.7 metaphlan
+conda activate mpa  # or source activate mpa
+metaphlan --install  # install db
+```
+
+## Run
+
+You can try the following tutorials:
+
+* [Metaphlan3](https://github.com/biobakery/MetaPhlAn/wiki/MetaPhlAn-3.0#basic-usage)
+* [StrainPhlan3](https://github.com/biobakery/MetaPhlAn/wiki/StrainPhlAn-3.0#usage)