Update slimux.vim

Added s:GetBuffer() and SlimuxREPLSendBuffer for sending whole buffer. I don't know Vim Script, so there might be useless code there. I was tired of ggVG<Leader>s<C-o><C-o>.
Add SlimeSendRange to resolve issue #24

SlimeSendRange function concatenates the lines in the range of
interest (working with the usual vim verb like syntax), and then
sends them using SlimuxSendCode.  No change to user keybindings
required.
Merge branch 'range' of https://github.com/dvbuntu/slimux
Merge branch 'master' of https://github.com/flexdec/slimux

Conflicts:
	plugin/slimux.vim