Fork multibase and nom_locate to disable std default feature in Cargo.toml

[samuelburnham]

In order to add no_std compatibility to the above yatima_core dependencies, the easiest approach is to fork them and change a few lines in their Cargo.toml. It seems like multibase and nom_locate were meant to be used in a no_std environment with cargo build --no-default-features, but this didn't work for me when using them as a dependency.

Relevant to #38.