Bump hamcrest to 0.1.5

[Eijebong]

The main change is that the assert_that function is now deprecated and
is replaced by the assert_that! macro hence the size of that patch.
Since that macro needs some traits to be in scope, I changed every
hamcrest import to be just use hamcrest::prelude::*.

[rust-highfive]

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[alexcrichton]

Thanks! I've sort of personally been content to stick to an older version because it works for us and I'm not sure there's much active development upstream to take advantage of. If we're consdering large changes to the test suite I think it's worth considering just dropping this dependency altogether. IIRC we only use one or two small features and we could relatively easily vendor them into cargotest perhaps?

[matklad]

@alexcrichton yeah, I personally never was thrilled by fluent assertion libraries. It seems simpler to just use assert! most of the time and switch to hand-crafted assetion messages and diffing functions for complex cases. So, +1 from me to keeping status quo or dropping the dependency.

(Interestingly, what I find useful is py.test style supercharging of the build-in assert, and we might get something similar once rust-lang/rfcs#2011 is implemented).

[bors]

☔ The latest upstream changes (presumably #4770) made this pull request unmergeable. Please resolve the merge conflicts.

[Eijebong]

Sure. I was just trying to reduce the number of old dependencies in cargo ^_^
If you'd prefer to rewrite all the test suite without harmcrest, that's fine by me (maybe I'll try to do it someday if I find the motivation)