rinari-highlight-keywords shouldn't use font-lock-keyword-face

[dgutov]

In a certain package I'm writing, I need a way to know quickly if the symbol on point is an actual Ruby keyword. Since ruby-mode doesn't have a separate constant for them, I have to check against the face text property, and the current highlighting throws me off.

Alternative suggestions: font-lock-builtin-face, font-lock-preprocessor-face.

[purcell]

Done, and this looks better too. :-)

[dgutov]

Thanks!