Add godef_newtab
Add docs for godef_newtab
Allow usage on modified buffers
Merge pull request #8 from hoelzro/master

Fix issues #6 and #7
keep the window split config in a single variable

Having godef_split *and* godef_newtab confuses your ~/.vimrc.  Having
magic numbers is only slightly less ugly, but preferable for the moment.
I'll replace this with string constants at some point in the future.
Something more like "g:godef_splitmode='tab'" or whatever.