Among other benefits (i.e. correct fall back to ascii theme when Vim uses
non-unicode encoding) this should also fix travis tests: apparently travis is
not setting LANG or similar environment variables to some unicode locale, so
tests are failing.
dark_green_gray gradient was generated with
tools/generate_gradients.py 70 247
. It is used for non-insert modes in the current window. light_green_gray
gradient was generated with
./tools/generate_gradients.py 148 250
. It is used for insert mode in the current window.