Don't remove H atoms when drawing Hydrogen bonds

This was added in PR #1961 which indroduced
the ability to draw hydrogen bonds.
It was removed without explanation in
ec95153
which made drawing work for fragments.
That broke drawing of hydrogen bonds.
The unit test for drawing hydrogen bonds exists,
but just checks that a PDF is made, not
what it looks like. So this wasn't detected.

Author: rwest

rmgpy/molecule/draw.py

@@ -184,7 +184,8 @@ def draw(self, molecule, file_format, target=None):
         surface_sites = []
         for atom in self.molecule.atoms:
             if isinstance(atom, Atom) and atom.is_hydrogen() and atom.label == '':
-                atoms_to_remove.append(atom)
+                if not any(bond.is_hydrogen_bond() for bond in atom.bonds.values()):
+                    atoms_to_remove.append(atom)
             elif atom.is_surface_site():
                 surface_sites.append(atom)
         if len(atoms_to_remove) < len(self.molecule.atoms) - len(surface_sites):