Using relative paths rather than absolute

[maxsam4]

Currently, the path included in the event that is added by the instrumenter is an absolute path which can be huge.

Our instrumented contracts at https://github.com/PolymathNetwork/polymath-core have now become so big due to the absolute paths that they are failing to compile. They instrument and compile just fine if I move the project folder nearer to the root of the system as the absolute path becomes shorter.

I am not sure why absolute paths are currently being used over relative paths. I can provide a set of instrumented contracts that are failing to compile due to huge absolute path, if required.

Update: I have created a PR to fix this.

[cgewecke]

In work planned for 0.7.0 (see #346) we will use an in-process memory to track file locations. Instrumentation will consist of a hash to those values.

Implementation detail: nyc issue 110: Relative paths in the coverage file are in violation of istanbul spec

[cgewecke]

Published w/ 0.7.0