Make SlimeSendLines honour g:slime_default_config.

The merge that added g:slime_default_config added SlimeGetConfig calls
to SlimeSendOp and SlimeSendRange, but not to SlimeSendLines. Thus the
latter did not use defaults if they were set. This change corrects that.
Merge pull request #42 from mhoogendoorn/master

Make SlimeSendLines honour g:slime_default_config.