fix: syntax error if ctermbg length is not 3
Make sure to execute git in the directory of the current file.

This fixes a problem where wrong gutter markers would appear after navigating
to another place with e.g. 'gf'.
Merge remote-tracking branch 'justinmk/master' into daily-use
fixed @x bug in ctermbg fix
Merge pull request #16 from Droggelbecher/master

Fix git execution with wrong working directory
fixed ctermbg metch bug
Better hi parsing

Previous code set some expectations on the highlight command output which not
always are true. It exptected `ctermbg` to be exactly 3 chars long and `guibg`
to be exactly 7 chars long. This is not true for many cases. Here's for example
my `SingColumn`:

    SignColumn     xxx term=standout ctermfg=11 ctermbg=8 guifg=Cyan guibg=Grey

New code sets a different sets of expectations that might be a bit better. New
code relies on the normalized output of `highlight` command. It parses output
and takes the part from "=" to the first space. This should cover the case of
varying length of numeric colours as well as named colours.