Added user guide and bibliography entry

docs-source/usersguide/application.rst

@@ -725,6 +725,8 @@ File                           Force Field
 :code:`amber99sbnmr.xml`       Amber99SB with modifications to fit NMR data\ :cite:`Li2010`
 :code:`amber03.xml`            Amber03\ :cite:`Duan2003`
 :code:`amber10.xml`            Amber10 (documented in the AmberTools_ manual as `ff10`)
+:code:`amberfb15.xml`          AMBER-FB15\ :cite:`Wang2017`. Intramolecular parameters optimized with
+                               ForceBalance using high-level ab initio data.
 :code:`amoeba2009.xml`         AMOEBA 2009\ :cite:`Ren2002`.  This force field is deprecated.  It is 
                                recommended to use AMOEBA 2013 instead.
 :code:`amoeba2013.xml`         AMOEBA 2013\ :cite:`Shi2013`

docs-source/usersguide/references.bib

@@ -495,3 +495,15 @@
    year = {2014},
    type = {Journal Article}
 }
+
+@article{Wang2017
+   author = {Wang, Lee-Ping and McKiernan, Keri A. and Gomes, Joseph and Beauchamp, Kyle A. and Head-Gordon, Teresa and Rice, Julia E. and Swope, William C. and Martínez, Todd J. and Pande, Vijay S.},
+   title = {Building a More Predictive Protein Force Field: A Systematic and Reproducible Route to AMBER-FB15},
+   journal = {Journal of Physical Chemistry B},
+   volume = {0},
+   number = {ja},
+   pages = {null},
+   year = {2017},
+   type = {Journal Article}
+   doi = {10.1021/acs.jpcb.7b02320},
+}