Deft mode should special mode-class

As per the Emacs major mode conventions, if a mode "is appropriate only
for specially-prepared text produced by the mode itself (rather than by
the user typing at the keyboard or by an external file), then the major
mode command symbol should have a property named `mode-class` with value
`special`..."
Update deft-strip-title-regexp

Now includes Emacs mode declarations of the form -*-mode-*- and LaTeX comments.
Remove leading and trailing whitespace from titles
Read file local variables after opening

Call hack-local-variables after loading deft-text-mode.