Some basic buildpack specs
Tests for hooks
Raise exception if hook script doesn't exit with 0
Log output of hook script
Remove invalid reference
Dump buildpack.log on compile failure
Tidy up compile error reporting
Tidy up compile error reporting
Pass build_dir to hook scripts
Fix syntax error
Add pre_runtime_compile and post_runtime_compile
Output hook time taken
Don't print anything during detect and release steps
Add sample with hooks
Update tests
Merge pull request #16 from mrdavidlaing/master

Add extension points - implementation, closes #16