Don't rebind C-x C-a in emacs-lisp-mode: it upsets edebug

Fixes #173
Check OS before using exec-path-from-shell for $LEDGER_FILE

See #174
Update README to clarify steps to follow before filing issues
Merge remote-tracking branch 'upstream/master'
merge upstream
yasnippet 可以使用了。
yasnippet 可以使用了。
done by st shell