remove timestamp line from compiled snippets file

better for version control; no spurious changes
add missing sed command
fix bugs in create_stan_lang.py from hardcoding files
handle increment_log_prob snippet separately
updated language
Merge branch 'develop' into feature/auto-complete

Conflicts:
	Makefile
	snippets/stan-mode/.yas-compiled-snippets.el
move auto-complete code into stan-mode
refactor use of code conditional on stan-turn-on-imenu
require auto-complete-config to be loaded
rename options for imenu-mode
Merge branch 'develop' into feature/auto-complete

Conflicts:
	stan-mode.el
rename stan-turn-on-auto-complete to stan-use-auto-complete