Use the new 'feedkeys' API function for Neovim
Fix @end directive when the buffer only has 1 line

The previous test was `if not self._line`, which caused `EnsureAtEnd` to raise
an exception for buffers with 1 line since 0 is a falsy value
Merge pull request #45 from tarruda/use-feedkeys

Use feedkeys for Neovim mode and fix bug with @end directive