Release 0.5.0

This release includes
- Changing output asserts
  - `.prints` -> `.stdout().contains`
  - `.prints_exactly` -> `.stdout().is`
  - `.prints_error` -> `.stderr().contains`
  - `.prints_error_exactly` -> `.stderr().is`
- Add negative output assertions
  - `.stdout().isnt`
  - `.stdout().doesnt_contain`
- Output assertions are now anded together rather than replacing each
  other.

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "assert_cli"
-version = "0.4.0"
+version = "0.5.0"
 description = "Test CLI Applications."
 authors = ["Pascal Hertleif <[email protected]>"]
 license = "MIT OR Apache-2.0"