Change build and clean to get target from package.json

[raythree]

Changed build and clean to get target configuration and webpack public paths from package.json.

[coveralls]

Coverage remained the same at 94.595% when pulling 5a4feb792558fa615c00cbd70bcfcb26157d4da9 on raythree:build-config-changes into 134b5f9b7dfcc3619a2af604e824f539b386ea47 on coryhouse:master.

[coveralls]

Coverage remained the same at 90.476% when pulling bcd13c452fbe6cb035ea69a9f53988579cf71c70 on raythree:build-config-changes into 15963df1cb511add2e6ee7b16cdaf6441e02754d on coryhouse:master.

[coveralls]

Coverage remained the same at 90.476% when pulling 0aac32ec784208b349842ff945ae65991c552d62 on raythree:build-config-changes into b69802f507a6ec3aa61c0565714ac16ce773d0a5 on coryhouse:master.

[m10]

it would be nice if these configs would be asked during setup