Improve coverage #2

[dvermd]

This PR is based on the PR #207

• Add the ability to deserialize HashMaps from Tape.
• Add some more tests as part of Improve testing #57
• Do not run coverage on test code

[dvermd]

It seems that the code coverage is tagged as decreased because it uses the number of lines as metrics. With the --ignore-tests option of tarpaulin, there are less lines that are to be covered. Looking at Coveralls report, we can that the relevant column decreased just like the covered one.

If you want to review this change in its own PR to better see the coverage improvements of the other commits, let me know and I'll split the PR.

[Licenser]

Sorry for the late reply :) this looks great I'll update the branch and see if that solves the clippy complaining

[Licenser]

Seems update was not enough :) can you address the clippy issues and then we can merge this :D

[dvermd]

I had a hard time finding the clippy warnings the previous commits added. So I fixed most of the clippy warnings (most of them by clippy --fix).
The remaining warnings are from json! and json_typed! macro that swallow the error on inserting a (key, value) pair to a Value. I don't know how you want to handle this one but I think hiding the error this way will be misleading at some point for a user.

This one is also not addressed by this commit

warning: casting `i64` to `u64` may lose the sign of the value
  --> src/sse42/stage1.rs:76:17
   |
76 |         let b = -1_i64 as u64;
   |                 ^^^^^^^^^^^^^
   |

[Licenser]

👍 awesome, I think leaving that out for now is fine. the let _ = ...insert in the macros isn't swallowing errors but rather swallowing the return value as we already know that the object is an object, and the content is a value since it's created by a macro :)