Now when trying to open files and buffers it will use the `buffer`
command when there is an existing buffer with the same name. This will
allow us to open non file buffers like terminals and log buffers.
By using the `bufnr` function to get the existing buffers, it will also
work for buffers that have been renamed with `title` command
Ref: #31
When reading the output of a command we are now reading the stream line
by line and building the table of results. This will save us a loop of
the results later, if we returned a string we need to split the string
before adding each line to the completion buffer because nvim only
supports replacing one line at a time.
This makes the terminal go really funkie and sometimes crash when
printing the error messages to the current process stdout where nvim is
running.
Now the error output is sent to the `popen` output and displayed in the
ivy completion buffer without messing with the current process io.
Now you can open the currently selected item in a vertical split or a
horizontal split. The completion callback must support the current
actions.
There is also a bit of testing in here. The vim mock has been refactored
and split out so we can use it multiple tests.
