Make it work on Mac VIM, whitespace trim option

# Changes
* FIX: due to mixed newline encodings, VIM 7.4.161 raised errors => converted .vim files to utf-8 / unix line endings.
* FIX: corrected filetype detection for *.asc
* FEATURE: added detection of *.ad files as asciidoc
* FEATURE: added option g:asciidoc_trim to trim trailing whitespaces on save (useful when versioning files)