As reported in the issue #380, the current parser emits an error on parsing a floating point value which ends with a dot.
That is because, while scanning a parsed scalar, the parser mistakenly assumes decimals after a dot.
However, the spec explicitly allows omitting decimals after a dot here as the regular expression for the float tag.

So, this PR has fixed implementation to follow the spec, and the updated parser now correctly parse such floating point values.
To validate the changes, some relevant test cases have also been added to the test suite.

Pull Request Checklist

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• Changes are described in the pull request or in a referenced issue.
• The test suite compiles and runs without any error.
• The code coverage on your branch is 100%.
• The documentation is updated if you added/changed a feature.

Please don't

• The C++11 support varies between different compilers and versions. Please note the list of supported compilers. Some compilers like GCC 4.7 (and earlier), Clang 3.3 (and earlier), or Microsoft Visual Studio 13.0 and earlier are known not to work due to missing or incomplete C++11 support. Please refrain from proposing changes that work around these compiler's limitations with #ifdefs or other means.
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