Remove --all-features

[Manishearth]

Fixes the build

This was broken by rust-lang/cargo#7507 , but the previous behavior was that the flags were ignored, so I removed them

r? nox @ferjm

[nox]

@bors-servo r+

[bors-servo]

📌 Commit 740551a has been approved by nox

[bors-servo]

⌛ Testing commit 740551a with merge 3f89925...

[bors-servo]

💔 Test failed - checks-travis

[CYBAI]

error: target `play_media_stream` in package `examples` requires the features: `player`

Consider enabling them by passing, e.g., `--features="player"`

error: target `play_noise` in package `examples` requires the features: `noise`

Consider enabling them by passing, e.g., `--features="noise"`

error: target `simple_player` in package `examples` requires the features: `player`

Consider enabling them by passing, e.g., `--features="player"`

error: target `simple_webrtc` in package `examples` requires the features: `webrtc`

Consider enabling them by passing, e.g., `--features="webrtc"`

[Manishearth]

@bors-servo r=nox

trying explicit features

[bors-servo]

📌 Commit a9d9a5e has been approved by nox

[bors-servo]

⌛ Testing commit a9d9a5e with merge 09eefc6...

[bors-servo]

💔 Test failed - checks-travis

[Manishearth]

rust-lang/cargo#7525