libskycoin v0.25.1-rc3

Added

• Export functions in Skycoin 0.25.1 core API's
• skyapi C client for Skycoin node REST at lib/curl.
• Support for building libskycoin on ARM and 32 / 64 bits.

Fixed

• /api/v1/health will return correct build info when running Docker containers based on skycoin/skycoin mainnet image.

Changed

• Adapt libskycoin after switching skycoin-cli from urfave/cli to spf13/cobra.

Removed

• Delete function SKY_base58_String2Hex