[subset] Add --glyphs
[subset] Accept separate on whitespace as well as comma

For all options, including the newly added --glyphs.
[subset] Minor
[subset] allow for unicode-based name with suffixes in the subset list

Fixes https://github.com/behdad/fonttools/issues/133

That part of the code is becoming really messy, but I want to get
all the features in first, then clean up.
Allow passing encoding to XMLWriter()

We don't support non-UTF-8 encodings, but reinstate the argument
such that existing code, like robofab, continues to work.
[subset] Add --unicodes and --unicodes-file

Fixes https://github.com/behdad/fonttools/pull/79
[subset] Accept unicode ranges

Eg --unicodes=41-5a,61-7a to choose ASCII letters.  Note that with
this, --unicodes-file accepts fontconfig .orth files that do not
include other files.
[subset] "Support" VDMX

VDMX doesn't have glyph-specific data, so pass it through if requested.
We can actually load the table now, but it needs no subsetting anyway.
[subset] Fix --unicodes doc
[subset] Add --gids that takes list of glyph ids or ranges

Fixes https://github.com/behdad/fonttools/issues/113
[subset] Add --ignore-missing-glyphs and --no-ignore-missing-unicodes

Move glyph checking into the subsetter.  Also fix --gids.  Previous
patch's implementation was wrong as it was picking up glyphs from
sorted glyph-name list, NOT the glyph order!

Fixes https://github.com/behdad/fonttools/issues/34
[subset] Remove special handling of gidNNN, uniXXXX

We now have --gids and --unicodes, so only accept glyph names
on cmdline.  Cleans up a few things.

Sorry about the breakage in advance everyone. :)