Improve gruvbox with C code

Hi,

here are two small improvements. The first makes it easier to identify strings and the second displays compile errors/warnings more prominent. See the two pictures below:

gruvbox string improvement -> http://min.us/i/WV09c3thkZ1A
gruvbox error improvement ->http://minus.com/i/bpBizN0WkXLOJ

 -- asn