Feature matrix & conditioned doc generation

- Ensures that library builds and passes all tests without any
  features and with `tlsv1_1`, `tlsv1_2` features enabled. Note, 
  that `sslv2` isn’t in test case because on modern linux (like 
  on Travis servers) `SSLv2_method` isn’t in `libssl.so` so it
  builds fine but fails on linking tests.

- For simplification it generates docs after every build, but 
  uploads them once - if it is `master` branch and not a pull
  request.

.travis.yml

@@ -2,16 +2,20 @@ language: rust
 env:
   global:
     - secure: qLvBJoJOJcPPZ+e31175O6sMUGBHgHe/kBuI0FCPeifYmpFyeRAkEvGddEkf8t3rojV+wE14CNYzzGsT/W/+JY7xW0C1FQKW3r+8SZ1Cave/8ahee0aCQVXGf0XY8c52uG6MrLGiUlNZbOsyFSdFUc/Io+kYZas4DxrinRSOIEA=
+  matrix:
+    - FEATURES=""
+    - FEATURES="tlsv1_1 tlsv1_2"
 os:
   - osx
   - linux
 before_script:
   - openssl s_server -accept 15418 -www -cert test/cert.pem -key test/key.pem >/dev/null 2>&1 &
 script:
-  - cargo build
+  - cargo build --features "$FEATURES"
-  - cargo test
+  - cargo test --features "$FEATURES"
-  - rustdoc src/lib.rs
+  - cargo doc --features "sslv2 tlsv1_1 tlsv1_2"
-  - cargo build --features "sslv2"
+after_success: |
-  - cargo build --features "tlsv1_1 tlsv1_2"
+  [ $TRAVIS_BRANCH = master ] &&
-after_script:
+  [ $TRAVIS_PULL_REQUEST = false ] &&
-  - curl http://www.rust-ci.org/artifacts/put?t=$RUSTCI_TOKEN | sh
+  cd target/doc &&
+  (curl http://www.rust-ci.org/artifacts/put?t=$RUSTCI_TOKEN | sh)