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] Fix subsetting of Khmer fonts

Read comment.
Minor optimization of table loading

Is both faster and more memory efficient.
Further optimize table loading

Again, both faster and more memory efficient
Handle NULL coverage table in ligature substitute

Just to be in line with Single and Alternate subst.
Compute correct LookupType when compiling font

Also ensures that all subtables of a lookup have the same
lookup type.