Use ElementTree instead of cElementTree for parsing ivy files.
Use ElementTree instead of cElementTree for parsing ivy files.

The performance penalty is infinitesimal and cElementTree isn't
always available, apparently.

Auditors: pl

abel-von/commons,pombredanne/commons,Yasumoto/commons,VaybhavSharma/commons,VaybhavSharma/commons,pombredanne/commons,nkhuyu/commons,pombredanne/commons,abel-von/commons,pombredanne/commons,pombredanne/commons,cevaris/commons,ericzundel/commons,cevaris/commons,atollena/commons,ericzundel/commons,atollena/commons,ericzundel/commons,Yasumoto/commons,VaybhavSharma/commons,cevaris/commons,atollena/commons,jsirois/commons,WCCCEDU/twitter-commons,cevaris/commons,VaybhavSharma/commons,jsirois/commons,cevaris/commons,ericzundel/commons,abel-von/commons,jsirois/commons,VaybhavSharma/commons,nkhuyu/commons,atollena/commons,ericzundel/commons,brutkin/commons,Yasumoto/commons,brutkin/commons,Yasumoto/commons,brutkin/commons,jsirois/commons,WCCCEDU/twitter-commons,brutkin/commons,nkhuyu/commons,WCCCEDU/twitter-commons,abel-von/commons,WCCCEDU/twitter-commons,brutkin/commons,nkhuyu/commons,nkhuyu/commons,Yasumoto/commons,WCCCEDU/twitter-commons,jsirois/commons,abel-von/commons,atollena/commons