The rule correctly reports number values like `.1`, `1e2`, `.NaN` and
`.Inf`, but it also reported false positives on strings like `.1two3`,
`1e2a`, `.NaNa` and `.Infinit∞`.
The regexps need to end with an end delimiter (`$`) otherwise longer
strings can be matched too.
Fixes https://github.com/adrienverge/yamllint/issues/495