smart_auto_mappings: look for `from` only at the start of a line
smart_auto_mappings: look for `from` only at the start of a line

Fixes https://github.com/davidhalter/jedi-vim/issues/469.
Closes https://github.com/davidhalter/jedi-vim/pull/470.

davidhalter/jedi-vim,FBruynbroeck/jedi-vim,wilywampa/jedi-vim,genzj/jedi-vim