Fix `yas-reload-all' call

This was not getting ran because "yasnippet", not "yas", should be
passed to `eval-after-load'. But using `eval-after-load' here is
pointless because `prog-mode-hook' will be called during initialization
anwyway.
Remove unnecessary lambdas from yas hooks
Add function to find PDF for TeX file
Change {forward,backward}-paragraph keybinding
Ignore abbrev_defs file