Placing `yas/hippie-try-expand' at the end of the
`hippie-expand-try-functions-list' doesn't seem to work very well and
putting it in the front might cause situations where I want to expand
a variable name or something and yas might take over, so don't use yas
with hippie-expand. Instead bind `yas-expand' to `C-\' and set
`yas-fallback-behavior' to nil so it doesn't start acting crazy when
there's no snippet to expand.
