Updated package prerequisites to address aerospike/aerospike-client-nodejs#107
Updated package prerequisites to address aerospike/aerospike-client-nodejs#107

* Updated gcc version dependencies to note that gcc 4.8 or later is
  required to build package using Node.js v4/5.
* Added note on requirement to install updated CentOS/REHL dev tool chain.

aerospike/aerospike-client-nodejs,aerospike/aerospike-client-nodejs,aerospike/aerospike-client-nodejs,aerospike/aerospike-client-nodejs,aerospike/aerospike-client-nodejs