Added pkpass to the list
do not override custom excerpt set in YAML frontmatter

Fixes #933.
Add tests for using custom excerpt
fix indentation of test
rework excerpt to be an accessor method

Instead of setting self.excerpt, make it a method
that returns either the custom excerpt or the pre-
viously extracted excerpt.
remove useless attr_reader for excerpt (is a method now)
new test: ensure the correct excerpt is exposed to liquid

Also shorten test code a little bit.
do not allow markdown etc. in excerpt

Adjust the tests accordingly. Also
add a message for one of the tests.
one more indentation fix
Merge pull request #945 from voidfiles/master

Accept multiple config files from command line
Update history to reflect merge of #945
Merge pull request #946 from maul-esel/preserve_excerpt

Preserve 'excerpt` in YAML Front-Matter
Update history to reflect merge of #946.
expose file path relative to source dir to liquid

Fixes #633.
fix path for posts: must include "_posts"
add cucumber tests for page.path variable
Remove code duplication
Add TomDoc for Jekyll::Command.process_site
Move Jekyll::DEFAULTS to Jekyll::Configuration::DEFAULTS
Add Jekyll::Configuration