Publish 0.7

This publish includes:

- Signal Map and ZipMap RustAudio#68
- impl Signal for Box<Signal> RustAudio#67
- Change Signal::next return type from Option<Frame> to Frame RustAudio#57
- Make `Bus` more memory efficient RustAudio#58

Author: mitchmindtree

Cargo.toml

@@ -1,8 +1,7 @@
 [package]
-
 name = "sample"
 description = "A crate providing the fundamentals for working with audio PCM DSP."
-version = "0.6.2"
+version = "0.7.0"
 authors = ["mitchmindtree <[email protected]>"]
 readme = "README.md"
 keywords = ["dsp", "bit-depth", "rate", "pcm", "audio"]