message: add getTransactionInfo
diff: @@ -115,6 +115,18 @@ class BlockstackNetwork {
  })
  }
  + getTransactionInfo(txHash: string) : Promise<{block_height: Number}> {
  + return fetch(`${this.utxoProviderUrl}/rawtx/${txHash}`)
  + .then(resp => {
  + if (resp.status === 200) {
  + return resp.json()
  + } else {
  + throw new Error(`Could not lookup transaction info for '${txHash}'. Server error.`)
  + }
  + })
  + .then(respObj => ({ block_height: respObj.block_height }))
  + }
  +
  getFeeRate() : Promise<number> {
  return fetch('https://bitcoinfees.earn.com/api/v1/fees/recommended')
  .then(resp => resp.json())
  