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.
touch up README
SlimeSend calls SlimeGetConfig
Remove buffer when sending text with tmux.

Tmux keeps its buffers as a stack. Without this patch, every time a selection
is sent to tmux, one buffer will be added. By adding the "-d" option to 'tmux
paste-buffer', the buffer is released.
Merge pull request #45 from geertj/master

Remove buffer when sending text with tmux.
Merge branch 'master' of github.com:jpalardy/vim-slime

* 'master' of github.com:jpalardy/vim-slime:
  Remove buffer when sending text with tmux.
  SlimeSend calls SlimeGetConfig
  touch up README
  Make SlimeSendLines honour g:slime_default_config.