Allow access to getrawmempool verbose mode

[dabura667]

This will give access to the ancestorsize and ancestorfees for txes in the mempool.

I am using this to implement CPFP needed fees api for insight-api

[coveralls]

Coverage remained the same at 100.0% when pulling 076af38 on dabura667:master into da5d5ec on bitpay:master.

[dabura667]

Note: Starting with bitcoin core 0.13.0, a new RPC call was added called getmempoolentry

If bitcore would support >=0.13.0 bitcoin Core, then we could add support for that to make my PR for CPFP support in insight-api a lot more efficient.

bitpay/insight-api#508

bitcoin-cli getmempoolentry ebf88e8aede968e8bd70e91f2e9400523157b42af06a96a207bfeb1b18866495
{
  "size": 225,
  "fee": 0.00027120,
  "modifiedfee": 0.00027120,
  "time": 1493777210,
  "height": 464590,
  "startingpriority": 0,
  "currentpriority": 0,
  "descendantcount": 1,
  "descendantsize": 225,
  "descendantfees": 27120,
  "ancestorcount": 4,
  "ancestorsize": 902,
  "ancestorfees": 108480,
  "depends": [
    "ee466a87cd2447cd0564a1f703a145e376ab32cffd6562e19bb610b980f7d7e8"
  ]
}