replace hl color with a more distinguishable color

Because it's hard to distinguish hl color and hl-line color, especially
when just marking part of one line.
So I replace hl color with selection color of Sublime Text's Monokai
Bright Theme.

Change-Id: I30ac9505c78db871a7cfe4dcbac8a9eb01f43c56
Merge pull request #17 from chptx/master

replace hl color with a more distinguishable color