Move minibufexpl to version 6.4.4

There an error where my splits get resized to being equal width or equal
height when navigating between them. It seems to be an issue with
minibufexpl and the error is not present in this version.
Change url of tagbar.
Map jk to escape key. Minibufexpl filetype.

Also turned off numbers' filetype detection. The older verion of
minibufexpl doesn't report its filetype so that doesn't work anymore.