This change is an attempt to address the common problem of json number
unmarshalling where any number is converted into a float64 and
represented in a scientific notation on a marshall call. This behavior
breaks things like: chart versions and image tags if not converted to
yaml strings explicitly.

An example of this behavior: k8s failure to fetch an image tagged with a
big number like: $IMAGE:20190612073634 after a few steps of yaml
re-rendering turns into: $IMAGE:2.0190612073634e+13.

Example issue: https://github.com/helm/helm/issues/1707

This commit forces yaml parser to use JSON modifiers and explicitly
enables interface{} unmarshalling instead of float64. The change
introduced might be breaking so should be processed with an extra care.

Due to the fact helm mostly dals with human-produced data (charts), we
have a decent level of confidence this change looses no functionality
helm users rely upon (the scientific notation).

Relevant doc: https://golang.org/pkg/encoding/json/#Decoder.UseNumberSigned-off-by: Oleg Sidorov <oleg.sidorov@booking.com>