Start adding pyftmerge tool to merge fonts
[merge] Implement a coule more tables
[merge] Implement a few more straightforward tables
[merge] Implement OS/2 and cmap

Works for basic font mergin now.  Next: GSUB/GPOS/GDEF!
[merge] Whitespace
[merge] Implement --verbose and --timing
[merge] Remove unused code
[merge] Pass Merger down to merge() methods
[merge] Clean up imports
[merge] Minor
[merge] Implement GDEF

Only if GSUB/GPOS were so simple too!
[merge] Drop glyf hints

Since we don't renumber functions or CVTs, we have to drop hinting
for now.
[merge] Expand glyf components before merging

Such that components are converted to glyph names before remapping.
[merge] Minor
[merge] Use reduce more often
[subset] Oops.  Remove debug prints
[subset] Work around OTS being stupid
Fix encoding conversion in CFF

Was broken with Python 3 and Salsa-Regular.otf for example.
[subset] Add more TODO items
[subset] Make sure objects are decompiled during subsetting

We need to ensureDecompiled() whenever an object is modified
before we look up any member of it.

Note that normally objects remaining decompiled until we try
to write them out is fine, except for when they depend on
font.getGlyphOrder().  This however, shouldn't normally happen
since if there's an object depending on the glyph list (eg. a
Coverage table), it should already have been process to subset
it according to the requested glyphs.  Or that's the idea at
least.  The few cases that were not handled are handled
explicitly now.

This was showing a bug when subsetting Cabin for example.