Merge branch 'release-v0.7.15-sys-v0.8.0' into release

.travis.yml

Cargo.toml

README.md

appveyor.yml

openssl-sys-extras/Cargo.toml

openssl-sys-extras/build.rs

openssl-sys-extras/src/lib.rs

openssl-sys-extras/src/openssl_shim.c

openssl-sys-extras/src/ssl_options.rs

openssl-sys/Cargo.toml

openssl-sys/src/lib.rs

openssl/Cargo.toml

openssl/build.rs

openssl/src/asn1/mod.rs

openssl/src/bio.rs

openssl/src/bio/mod.rs

openssl/src/bn/mod.rs

openssl/src/c_helpers.c

openssl/src/c_helpers.rs

openssl/src/crypto/dsa.rs