message: force availability of nightly features in cargo
  since we're technically using a "dev" version of cargo, nightly features
  won't be available unless we force them on
diff: @@ -7,7 +7,7 @@ use std::path::{Path, PathBuf};
  use std::env;
  use std::sync::Arc;
  -use cargo::core::{SourceId, Dependency, Source, Package, Workspace};
  +use cargo::core::{self, SourceId, Dependency, Source, Package, Workspace};
  use cargo::core::compiler::{DefaultExecutor, CompileMode, MessageFormat, BuildConfig, Executor};
  use cargo::core::package::PackageSet;
  use cargo::core::source::SourceMap;
  @@ -30,6 +30,7 @@ use Metadata;
  // and build a crate and its documentation
  // instead of doing it manually like in the previous version of cratesfyi
  pub fn build_doc(name: &str, vers: Option<&str>, target: Option<&str>) -> Result<Package> {
  + core::enable_nightly_features();
  let config = try!(Config::default());
  let source_id = try!(SourceId::crates_io(&config));
  @@ -117,6 +118,7 @@ pub fn build_doc(name: &str, vers: Option<&str>, target: Option<&str>) -> Result
  /// Downloads a crate and returns Cargo Package.
  pub fn get_package(name: &str, vers: Option<&str>) -> CargoResult<Package> {
  + core::enable_nightly_features();
  debug!("Getting package with cargo");
  let config = try!(Config::default());
  let source_id = try!(SourceId::crates_io(&config));
  