Only use fc_gene_name if there are missing neurons

* a small step on the way to making fc_sub_scoremat more generic
  with a view to moving it to nat.nblast where it could be used for any
  kind of neuron
Update to use functionality ported into nat.nblast
Add nat.nblast dependency to Travis config
Bump version and update DESCRIPTION
Merge pull request #20 from ajdm/nat.nblast_porting

Update to use functionality ported into nat.nblast
Merge branch 'master' of github.com:jefferis/flycircuit

* 'master' of github.com:jefferis/flycircuit:
  Bump version and update DESCRIPTION
  Add nat.nblast dependency to Travis config
  Update to use functionality ported into nat.nblast
Deprecate pop3dfc, switching to npop3d

* removes .plotted3d environment
refactor plot3dfc using plot3d.character
Add example for plot3dfc

* includes specification of colour and using soma=TRUE
Merge branch 'feature/remove-pop3dfc'

* feature/remove-pop3dfc:
  Add example for plot3dfc
  refactor plot3dfc using plot3d.character
  Deprecate pop3dfc, switching to npop3d

* closes #11
Depend on nat >=1.5.7 and nat.nblast >=1.2

* for refactored plot3dfc and plot3d.hclust etc
Bump version to 1.5