new feature: xml root element will be discovered if recordPath is not set
bugfix: newly introduced option projectTags was not working in 0.3.7
bugfix: txt defaulted to fixed-width (should be line-based)
bugfix: default recordPath for json was not working in 0.3.7
bugfix: default sheets option was broken (but xls, xlsx, ods is broken in OpenRefine >=2.8 anyway, see #4)
tests: added sample files and an ipython notebook for comprehensive tests of create option