[MINOR] Fix keras2dml tabs/spaces inconsistency
[MINOR] Fix keras2dml tabs/spaces inconsistency

Prevents conflict with some IDEs causing errors when mixing tabs and spaces

Closes #763.

niketanpansare/incubator-systemml,gweidner/incubator-systemml,gweidner/systemml,niketanpansare/systemml,niketanpansare/incubator-systemml,deroneriksson/systemml,niketanpansare/systemml,gweidner/incubator-systemml,deroneriksson/incubator-systemml,gweidner/systemml,niketanpansare/systemml,niketanpansare/incubator-systemml,gweidner/incubator-systemml,gweidner/systemml,deroneriksson/systemml,gweidner/systemml,deroneriksson/systemml,deroneriksson/incubator-systemml,apache/incubator-systemml,apache/incubator-systemml,apache/incubator-systemml,gweidner/incubator-systemml,niketanpansare/systemml,deroneriksson/incubator-systemml,deroneriksson/systemml,apache/incubator-systemml,apache/incubator-systemml,niketanpansare/incubator-systemml,apache/incubator-systemml,gweidner/incubator-systemml,gweidner/incubator-systemml,gweidner/systemml,niketanpansare/systemml,deroneriksson/incubator-systemml,deroneriksson/systemml,deroneriksson/systemml,gweidner/systemml,deroneriksson/incubator-systemml,deroneriksson/incubator-systemml,niketanpansare/systemml