Improperly split arguments

The provided arguments in this call:

`grunt task:arg1:"arg2 with spaces":"arg3 : blah"`

Should be split out into `"arg1"`, `"arg2 with spaces"`, and `"arg3 : blah"`, but they will actually be split out into `"arg1"`, `"arg2 with spaces"`, `"arg3`, and `blah"` because of the colon inside of arg3

I realize this is a bit of an edge case, and I've only encountered it as a problem this one time.

No file or test is named. Start by locating the argument-splitting logic for the `grunt task:...` syntax and reproduce the quoted argument containing a colon; done means the three intended arguments remain intact, including `arg3 : blah`.

Written by the indexing model from the issue text.