Try to decrease dependencies

[elichai]

The time it takes to compile this library is getting pretty long. especially on CIs.
This is a naive start to hopefully decrease compile time.
here I just disabled unused features in dependencies(just this removed around 80 lines in the Cargo.lock)

[koute]

Thanks for the PR!

1. From what I can see on Travis it looks like one of your changes might have broken compilation without a Cargo.lock file. (See the job which sets WITHOUT_CARGO_LOCK=1.) Could you please check it out?
2. Please split/squash your changes into two commits - one which changes the Cargo.toml, and one which changes the Cargo.lock. (In general I like to keep the Cargo.lock changes in a separate commit as later it's easier to browse through history, etc.) Besides this it looks good to me as long as (1) will be fixed!

[elichai]

FYI it seems weird to use danger_accept_invalid_certs where it could be a HTTPS_PROXY (in general that's a weird function)

[elichai]

Ok, it updated reqwests to a new version, so I had to update the whole Cargo.lock

Updating the cargo.lock without this PR results in:
1 file changed, 1090 insertions(+), 778 deletions(-)

With this PR:
1 file changed, 1010 insertions(+), 855 deletions(-)

Not a massive change, but a change non the less. (80 less insertions and 77 more deletions)

[elichai]

Seems like travis fails on cargo check --target=x86_64-apple-darwin
probably new version of backtrace-sys requires some system library that isn't there, why don't you run this test on osx?

[koute]

Ugh, it looks like a C compiler is necessary now while it wasn't necessary before; backtrace-sys really ought to not require a full cross toolchain just to run cargo check. -_-

But you have a good point. I've just removed the checks and just put them in their own dedicated jobs for OS X and Windows. We'll see how it goes.