message: Improve Context::add_zipfile_bytes()
  Specifically, make it possible to call it without moo-ving the data.
diff: @@ -181,6 +181,7 @@ impl Context {
  }
  use std::path;
  +use std::borrow::Cow;
  /// A builder object for creating a [`Context`](struct.Context.html).
  #[derive(Debug, Clone, PartialEq)]
  @@ -189,7 +190,7 @@ pub struct ContextBuilder {
  pub(crate) author: &'static str,
  pub(crate) conf: conf::Conf,
  pub(crate) paths: Vec<path::PathBuf>,
  - pub(crate) memory_zip_files: Vec<Vec<u8>>,
  + pub(crate) memory_zip_files: Vec<Cow<'static, [u8]>>,
  pub(crate) load_conf_file: bool,
  }
  @@ -251,6 +252,7 @@ impl ContextBuilder {
  /// Add a new zip file from bytes whose contents will be searched
  /// for resources. The zip file will be stored in-memory.
  + /// You can pass it a static slice, a `Vec` of bytes, etc.
  ///
  /// ```ignore
  /// #use ggez::context::ContextBuilder;
  @@ -258,8 +260,10 @@ impl ContextBuilder {
  /// .add_zipfile_bytes(include_bytes!("../resources.zip").to_vec())
  /// .build();
  /// ```
  - pub fn add_zipfile_bytes(mut self, bytes: Vec<u8>) -> Self {
  - self.memory_zip_files.push(bytes);
  + pub fn add_zipfile_bytes<B>(mut self, bytes: B) -> Self
  + where B: Into<Cow<'static, [u8]>> {
  + let cow = bytes.into();
  + self.memory_zip_files.push(cow);
  self
  }
  