Add glyf.Glyph.trim() that removes padding and if asked hinting
[subset] Always remove 'glyf' Glyph padding

Before we were only doing this, partially, if --no-hinting was requested.
Always remove padding.  More savings.
Fix reading XML for CBLC with external image files
[ttx] Always add raw=True attribute when dumping DefaultTable to XML

Needed to avoid surprises when we add new table implementations.
Recently we added VDMX table, and that broke build of projects using
VDMX with DefaultTable, eg:

https://github.com/behdad/fonttools/issues/151
Bump fontTools.version to 2.5

Followup to
https://github.com/behdad/fonttools/commit/2a60b441b041f1aae783ab3cc5ab36e0cd46e9ab#commitcomment-7532556