Merge pull request #3 from NeuroML/development

Merging development into master for v2beta1 release
Initial commit travis
test commit
test
minor
Merge branch 'development'

* development: (32 commits)
  Adding latest nml2 files copied from main nml2 repo
  Updating to latest examples, schema & comptype definitions from main NeuroML2 repo
  Using latest nml2 schema from main repo
  Syncing to main version of comptype defn from NeuroML2 repo
  changed population/input notation to list format; increased dt for speed; adjusted graph scale
  Adding more permeability units
  tabs->spaces in ghk example...
  added Cells and GHK example from NeuroML2/NeuroML2CoreTypes
  added ghk stuff to schema
  Adding substance/mol in dims/units to help SBML integration
  Latest nml2 dimensions file from main nml2 repo
  Updating to latest examples from main nml2 repo
  Using latest Channels.xml & scheema from main nml2 repo
  Ensuring neuroml standalone elements picked out in correct order
  Using LinkedHashMap<String,Standalone> for getAllStandaloneElements to preserve order
  changes in exception handling
  Adding some entries to NeuroMLElements, making all final & static
  Minor update to string for iCa: CONC_MODEL_CA_TOT_CURR
  Updated with latest form of fixedFactorConcentrationModel
  Commenting printing out every unit conversion, makes the log file explode
  ...