Enable docker profiles on travis.

[IRus]

Since travis supports docker inside build, we can enable docker profiles.

Also i renamed postgresdocker to postgres-docker for consistency with mysql-docker

[IRus]

Problems:

mysql-docker:

Tests in error: 
  ReturnTypesMappingIT.testNCHAR:265 » CayenneRuntime [v.4.0.M4-SNAPSHOT Dec 06 ...
  ReturnTypesMappingIT.testNCLOB:328 » CayenneRuntime [v.4.0.M4-SNAPSHOT Dec 06 ...
  ReturnTypesMappingIT.testLONGNVARCHAR:601 » CayenneRuntime [v.4.0.M4-SNAPSHOT ...
  ReturnTypesMappingIT.testNVARCHAR:907 » CayenneRuntime [v.4.0.M4-SNAPSHOT Dec ...
  DataContextIteratedQueryIT.testPerformIteratedQuery_resolve:207 » CayenneRuntime
  DataContextIteratedQueryIT.testPerformIteratedQuery_CommitWithinIterator:227 » CayenneRuntime

postgres-docker

  DataContextIteratedQueryIT.testPerformIteratedQuery_resolve:207 » CayenneRuntime
  DataContextIteratedQueryIT.testPerformIteratedQuery_CommitWithinIterator:227 » CayenneRuntime

[stariy95]

Hi @IRus!
Pull request #162 should help with DataContextIteratedQueryIT test failures.