Merge pull request #636 from OpenZeppelin/release/v1.5.0

v1.5.0

ethpm.json

 {
   "package_name": "zeppelin",
-  "version": "1.4.0",
+  "version": "1.5.0",
   "description": "Secure Smart Contract library for Solidity",
   "authors": [
     "Manuel Araoz <manuelaraoz@gmail.com>"

package.json

 {
   "name": "zeppelin-solidity",
-  "version": "1.4.0",
+  "version": "1.5.0",
   "description": "Secure Smart Contract library for Solidity",
   "scripts": {
     "test": "scripts/test.sh",