Release v0.8.3 - MAGE-TAB format support

This release of isatools implements new MAGE-TAB format read/write capability, including import and export between MAGE-TAB and ISA formats (ISA-Tab and ISA-JSON).

• MAGE-TAB import to ISA #203
• MAGE-TAB export from ISA #124
• Fixes issues #101, #177, #191, #205, #210, #221, #222, #222, #223, #226
• For more information on the known issues with this release, please check the documentation at http://isatools.readthedocs.org

This is a minor update to 0.8.2 to address ISA-Tab loading issues reported in #222, #223 and #226.