add tests for optical font size matching
adapt makefile to preferred CTAN zip scheme

according to Robin Fairbairns:

>    btw, the least error-prone format for the zip file is:
>
>      xyz.zip ->
>        xyz.tds.zip (if available)
>        xyz/
>          [actual distribution of package xyz]
avoid recursing into font dirs retrieved by kpse

minor speedup (some 16% with standard sized TL texmf), especially if the
directories are uncached.  as we take care of duplicate results from the
file scanner elsewhere this will not affect the list of fonts found.
stript trailing slashes before joining paths
filter pwd from texmf directories
add diagnostics for environment variables in luaotfload-tool
Merge pull request #114 from phi-gamma/master

directory handling; environment variables