Update IPython requirement in INSTALL.md.
Set data_dir correctly if Gourmet is frozen.
Migrate from py2exe to cx_Freeze.

cx_Freeze allows us to produce a usable stand-alone .msi installer
package, so we don't need NSIS anymore.

Fixes #731, and fixes #76
Use Python logging instead of printing a traceback.

Otherwise, the frozen Windows binary would crash because
of the attempt to print the traceback.
Remove NSIS related files.
Disable the PDFPrintPlugin under Windows as poppler doesn't work there.
Add more Windows building instructions to INSTALL.md.
Update CODING.
Update TODO, rename to TODO.md.