Fix a few bugs surfaced when used in winmanager.
1) Change "execute $" to "normal $"
2) Suppress "--No lines in buffer--" message on buffer rebuild.
3) Allow highlighting "inactive" buffers (i.e. files specified in Vim
args, but not opened yet)
Merge pull request #9 from rburny/master

Fix a few bugs surfaced when bufexplorer is used inside winmanager.