Merges the keybase and Ledger code from go-crypto (which is no more) into the SDK Adds support for Ledger into gaiacli Cherry-picks updated error handling from #1158
implement Int, Int256, Uint256 pass ci pass ci add to changelog, add boundcheck to test add comments, fix cli_test.go fix errors apply requested changes panics on New*WithDecimal fix Int.BigInt() fix stake tests * Panic on uint division-by-zero * Set ok=false on NewIntFromString, NewUintFromString failure * Nuke CircleCI caches