Quality of Life options for TomlTable and TomlValue

[johnkiddjr]

Fixes #27

This adds the functionality of IEnumerator to TomlTable, allowing you to iterate on the table without needing to reference the Entries property.

foreach (var item in table.Entries)
{
    ...
}

Becomes

foreach (var item in table)
{
    ...
}

This also adds an override on the ToString method for TomlValue to return the StringValue property.

TomlString stringValue; //or any other TomlValue
Console.WriteLine(stringValue.StringValue);

Becomes

TomlString stringValue; //or any other TomlValue
Console.WriteLine(stringValue.ToString()); // outputs the value of StringValue now

[coveralls]

coverage: 92.402% (-0.07%) from 92.47% when pulling d485db0 on johnkiddjr:master into acc83e1 on SamboyCoding:master.

[SamboyCoding]

I have no issues with the actual content of this pull request, so on that front, this is approved, but as per coveralls' comment above, the lack of unit tests for the enumeration and string values has resulted in coverage decreasing, which I'd rather avoid, if you wouldn't mind writing a couple tests to cover those cases -- though they really don't need it, it's easier to just enforce the rule of "test as high a percentage of the codebase as possible" rather than making case-by-case decisions.

[johnkiddjr]

Agreed, added tests to ensure ToString and StringValue are equal (done for both TomlString and TomlLong) and tests to check that iterated values are the same as values pulled directly from the dictionary.

[SamboyCoding]

Appreciate it! Assuming this CI run passes fine, I'll merge this then.

[SamboyCoding]

Right well the explicit interface implementation wasn't covered but I can live with that, merging.