title: Cargo fails to build openssl
body: <p>I'm building a web application using nickel.rs. Everything's going fine but when I execute <code>cargo run</code>, I get the following error because of the hyper dependancy:</p>
  
  <pre><code>   Compiling openssl-sys-extras v0.7.9
     Compiling openssl-sys v0.7.9
     Compiling openssl v0.7.9
  Build failed, waiting for other jobs to finish...
  failed to run custom build command for `openssl v0.7.9`
  Process didn't exit successfully: `/Users/menawi/Developer/rust/nickelodean/target/debug/build/openssl-66237fc32eb1ac40/build-script-build` (exit code: 101)
  --- stdout
  TARGET = Some("x86_64-apple-darwin")
  OPT_LEVEL = Some("0")
  PROFILE = Some("debug")
  TARGET = Some("x86_64-apple-darwin")
  debug=true opt-level=0
  HOST = Some("x86_64-apple-darwin")
  TARGET = Some("x86_64-apple-darwin")
  TARGET = Some("x86_64-apple-darwin")
  HOST = Some("x86_64-apple-darwin")
  CC_x86_64-apple-darwin = None
  CC_x86_64_apple_darwin = None
  HOST_CC = None
  CC = None
  HOST = Some("x86_64-apple-darwin")
  TARGET = Some("x86_64-apple-darwin")
  HOST = Some("x86_64-apple-darwin")
  CFLAGS_x86_64-apple-darwin = None
  CFLAGS_x86_64_apple_darwin = None
  HOST_CFLAGS = None
  CFLAGS = None
  running: "cc" "-O0" "-ffunction-sections" "-fdata-sections" "-g" "-m64" "-fPIC" "-o" "/Users/menawi/Developer/rust/nickelodean/target/debug/build/openssl-66237fc32eb1ac40/out/src/c_helpers.o" "-c" "src/c_helpers.c"
  ExitStatus(ExitStatus(256))
  
  
  command did not execute successfully, got: exit code: 1
  
  
  
  --- stderr
  src/c_helpers.c:1:10: fatal error: 'openssl/ssl.h' file not found
  #include &lt;openssl/ssl.h&gt;
           ^
  1 error generated.
  thread '&lt;main&gt;' panicked at 'explicit panic', /Users/menawi/.cargo/registry/src/github.com-88ac128001ac3a9a/gcc-0.3.26/src/lib.rs:818
  </code></pre>
  
  <p>I need openssl because my web application needs to make <code>https</code> requests. How can I fix this error? I've attached a copy of my <code>Cargo.toml</code> file below:</p>
  
  <pre><code>[package]
  name = "nickelodean"
  version = "0.1.0"
  
  [dependencies]
  nickel = "0.8.0"
  mustache = "0.7.0"
  rustc-serialize = "0.3.18"
  hyper="0.8"
  </code></pre>