e2e test fail

[xuwei-k]

https://travis-ci.org/trueaccord/ScalaPB/jobs/91336480#L1442

[error] /home/travis/build/trueaccord/ScalaPB/e2e/target/scala-2.10/src_managed/main/compiled_protobuf/com/trueaccord/pb/flat/FlatProto.scala:20: object Scalapb is not a member of package com.trueaccord.scalapb
[error]   com.trueaccord.scalapb.Scalapb.getDescriptor(),
[error]                          ^
[error] /home/travis/build/trueaccord/ScalaPB/e2e/target/scala-2.10/src_managed/main/compiled_protobuf/com/trueaccord/proto/e2e/custom_types/CustomTypesProto.scala:42: object Scalapb is not a member of package com.trueaccord.scalapb
[error]   com.trueaccord.scalapb.Scalapb.getDescriptor()
[error]                          ^
[error] /home/travis/build/trueaccord/ScalaPB/e2e/target/scala-2.10/src_managed/main/compiled_protobuf/com/trueaccord/proto/e2e/maps/MapsProto.scala:30: object Scalapb is not a member of package com.trueaccord.scalapb
[error]   com.trueaccord.scalapb.Scalapb.getDescriptor()
[error]                          ^
[error] three errors found
[error] (compile:compileIncremental) Compilation failed