Detect version mismatches of parity-scale-codec

[cmichi]

Closes #232.

CI currently fails because master fails (see #236 for the fix for that).

@Robbepop @ascjones Are you aware of any other dependencies of a contract which must be compatible with the ink! version of that dependency? scale-info?

[ascjones]

Yes the versions of scale-info should match

[cmichi]

That's the current output:

$ cargo run -- contract build --manifest-path /tmp/foo/Cargo.toml 
error: There are multiple `scale-info` packages in your project, and the specification `scale-info` is ambiguous.
Please re-run this command with `-p <spec>` where `<spec>` is one of the following:
  scale-info:0.3.0
  scale-info:0.6.0
ERROR: Mismatching versions of `scale-info` were found!
Please ensure that your contract and your ink! dependencies use a compatible version of this package.

Mismatches of parith-scale-codec and scale-info are detected.

[ascjones]

Looks good but CI failing with compilation error.

[ascjones]

CI fix merged to master so just needs merging in here

[ascjones]

Nice! This should save us a lot of time answering this common problem.