Fix matching of the "first line deleted" sign

Closes #112.
Doc: "update on focusgained" doesn't write to disk

References #113.
Add sy#util#run_in_dir to run system() within a specific directory

Signed-off-by: James McCoy <vega.james@gmail.com>
Replace all uses of "cd … && do_something" with sy#util#run_in_dir

Signed-off-by: James McCoy <vega.james@gmail.com>
Merge branch 'UNC-paths'

Closes #114
Fix locale setting for Chinese Windows versions

On the Chinese version of Windows, v:lang is "zh_CN", but execute
":language zh_CN" will fail and ":language chinese_china" must be used
to change the locale instead.

Closes #116.