Switch on testing for the book; fix #6

[ghost]

Run the tests with the following:

cargo build    # first build async_std
mdbook test -L ./target/debug/deps docs

The -L flag is needed so that external crates can be resolved in the tests.

[skade]

Wow, thanks already for that :).

[ghost]

I haven't tested the changes to the travis build but otherwise I think this is ready.

[skade]

This will fail ;). What's missing is a before_script similar to here: https://rust-lang-nursery.github.io/mdBook/continuous-integration.html

[ghost]

I'm not sure how to fix this latest error from mdbook test about multiple matching crates for async_std. I saw something similar locally but only once and it seemed to resolve itself. Any ideas? By the way, feel free to make whatever changes needed to this, stylistically or otherwise.

[ghost]

Note that this fixes #89.

[ghost]

I've had to modify the travis config to where, when the book should be built, we don't run cargo check but instead just run cargo test.

This might cause ci to not fail as quickly on the linux build but the problem is that running cargo check followed by cargo test produces two entries for async_std in ./target/debug/deps which then causes mdbook test to fail when trying to resolve extern crate async_std.

I don't know of another way to fix that issue. If this is an acceptable workaround then I think this PR is good to go.

[skade]

This needs to be updated to remove all uses of #[feature(async_await)]

[ghost]

I've removed the #[feature(async_await)] and squashed some of the commits.

[ghost]

I've rebased again and fixed the latest set of merge conflicts. /cc @skade @stjepang