v0.12.0 (2018-12-09)

• Upgrade to ODK Validate v1.10.3
  Issue #225, https://github.com/XLSForm/pyxform/issue/225
  [ukanga]
• Process only standard XLSForm sheets
  Issue #229, https://github.com/XLSForm/pyxform/issue/229
  [ukanga]
• Add relative referencing
  Issue #4, https://github.com/XLSForm/pyxform/issue/4
  [ukanga]
• Fix randomize with dynamic seed value throws error
  Issue #238, https://github.com/XLSForm/pyxform/issue/238
  [ggalmazor]
• Update choice filter JSON representation
  Issue #234, https://github.com/XLSForm/pyxform/issue/234
  [lincmba]
• Make sure that the json scheme is a valid json
  Issue #223, https://github.com/XLSForm/pyxform/issue/223
  [HaidarZ]
• Skip over non-strings when replacing smart quotes
  Issue #236, https://github.com/XLSForm/pyxform/issue/236
  [jnm]
• Updated outdated language reference xlsform.org url
  Issue #221, https://github.com/XLSForm/pyxform/issue/221
  [tinok]