Minimum support Rust version changed with 1.2.0

[mgeisler]

Hi all,

I wanted to contribute some code to clap, and got an unexpected build failure. I believe I've traced it back to the newly released unicode-segmentation version 1.2.0, which include code using the ? operator. That is, clap is testng with Rust 1.11.0 and the ? operator was stabilized in Rust 1.13.0 -- hence the build failure.

I searched on the users forum and found some discussions about how to handle changes in the minimum supported Rust version -- some seemed to think it should require a major version bump, others did not.

So while there seems to be no best practice here yet, I just wanted to make you aware of the change :-) Would you be interested in extending our Travis config to test with a known-good minimum supported Rust version? I suppose that will be 1.13.0 at the moment.

The clap issue: clap-rs/clap#845 (comment).
The commit that introduced the ? operator: aaf9da4#diff-dd3463da52dddbc4cbf510ba1b8c1fd2R715.