Update README.md to use pip3

README.md

@@ -42,14 +42,14 @@ cd ../../
 ## Possibly setup python dependencies (you may want to set up a virtual environement) using commands below
 # conda install "numpy>=1.14" "scipy>=1.1" "appdirs>=1.4"
 # conda install -c conda-forge "mdanalysis>=0.18" 
-# pip install "cadnano>=2.5.2.1"
+# pip3 install "cadnano>=2.5.2.1"
 
 git clone https://gitlab.engr.illinois.edu/tbgl/tools/mrdna
 cd mrdna
-pip install .
+pip3 install .
 cd ..
 
 # Finally update your bashrc so that your shell can find the ARBD binary
 echo "PATH=$BUILD_DIR/arbd/src:\$PATH" >> ~/.bashrc
 source ~/.bashrc
-```
\ No newline at end of file
+```