change line highlight colour from blue to grey

works well with "highlight_line": true, in user settings

Signed-off-by: Joshua Paling <joshua.paling@gmail.com>
change embedded javascript tag colour to match other html tags

Signed-off-by: Joshua Paling <joshua.paling@gmail.com>
change doctype colour to grey

Signed-off-by: Joshua Paling <joshua.paling@gmail.com>