whitespace cleanup, mention pip install --user

tools/replica/reorder_remd_traj.py

@@ -321,7 +321,8 @@ def get_canonical_logw(enefn, frametuple_dict, temps, nprod, writefreq,
               Configurational log-weight calculation requires pymbar.
               Here are some options to install it:
               conda install -c omnia pymbar
-              pip install pymbar
+              pip install --user pymbar
+              sudo pip install pymbar
 
               To install the dev. version directly from github, use:
               pip install pip install git+https://github.com/choderalab/pymbar.git