Fix variable names

Make the variable for handling files consistent and fix the
examples for customizations 2 and 3.
Merge pull request #46 from gpoo/patch-1

Fix variable names
MAINT, change standard for entrytypes and id
add note about API breakage
DOC: difference upper lower case
Merge pull request #53 from sciunto/type

MAINT, change standard for entrytypes and id
add user
Merge pull request #55 from sciunto/users

add user
BibTeX comma first syntax, now supported by the parser and allowed in the writer
merge changes from upstream codeline