Added `Workbook.current()` class method
Modified `Workbook` constructor to check if `fullname` is a COM object, if so build Workbook from it
Added `is_xl_object` to both platforms to check if the argument is a COM object (on Mac it just returns False)
Added mechanism to specify Excel instance on which `new_workbook` and `open_workbook` should act.
The changes should not affect the Mac version
Also tiny bug fix: expression `len(sys.argv) >= 2 and sys.argv[2] == 'from_xl' should have strict inequality.
Call UpdateScreen on Mac to clear what seems like selected cells
Show Errors as popup on Mac, closes issue #57 and closes issue #51
Implmented Range.autofit(), closes #33
Merge branch 'ericremoreynolds-master' into develop
made Workbook.current() cross-platform compatible
reimplemented _xlwindows._get_latest_app
require minimum version of psutil, closes #48
made atleast_2d work for scalars, closes #53
fixed _get_latest_app in case Excel has been closed
account for Excel 2010 array formatting bug (#43)
refactored Workbook.current() and renamed into Workbook.active()
added more tests
fixed chart tests on mac
renamed Workbook.active() back into current() so it doens't get confused with the ActiveWorkbook in VBA that refers to the active Window
moved xl_workbook_latest to platform modules
fixed tests
implemented Sheet class on mac
added Sheeet.name/index on windows and readded get_app() that was unintentionally deleted