verbose-errors feature isn't additive

[tmccombs]

Cargo features are supposed to be additive, but the verbose-errors feature completely changes the type of Err (and thus change IResult), which could cause compatibility issues between libraries that use verbose errors and those that don't. I'm not really sure what a good solution for this would be.

[Geal]

there is no way to change this by considering the feature as additive, it is just another version of the same crate