Fix function keyword as property name

[MaximSokolov]

#334 (comment)

// highlights the contents of the string correctly as a string:
{ func: 'function foo() { return "foo"; }' };
"things are ok";

// now it thinks the string contents are actually a function definition:
{ function: 'function foo() { return "foo"; }' };
"not ok... :("

Fixes:

foo: a => a
foo : a => a // bug