added yasnippet locally

needed to compile snippets
compile snippets
add auto-complete support
add auto-complete support
update makefile
Merge branch 'develop' into feature/auto-complete

Conflicts:
	Makefile
	snippets/stan-mode/.yas-compiled-snippets.el
	snippets/stan-mode/Range Constraints/bounds.yasnippet
	snippets/stan-mode/Range Constraints/lower.yasnippet
	snippets/stan-mode/Range Constraints/upper.yasnippet
	snippets/stan-mode/Range_Constraints/bounds.yasnippet
	snippets/stan-mode/Range_Constraints/lower.yasnippet
	snippets/stan-mode/Range_Constraints/upper.yasnippet
	snippets/stan-mode/lower.yasnippet
	snippets/stan-mode/lower_upper.yasnippet
	snippets/stan-mode/upper.yasnippet
improve documentation
reorder precedence of ac-sources
fix else snippet
Merge branch 'develop' into feature/auto-complete

Conflicts:
	snippets/stan-mode/.yas-compiled-snippets.el
ensure ac-dict is sorted
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