bindConfigHelpers method adds unwanted methods to helpers object

[bashleigh]

Issue type:

[ ] question
[x] bug report
[ ] feature request
[ ] documentation issue

nestjs-config version

@latest

@nestjs/common+core or other package versions

• @nestjs/common: 5.6.2
• @nestjs/core: 5.6.2

Excepted behavior

Classes to not be scanned for all methods

Actual behavior or outcome (for issue)

Currently the bindConfigHelpers method will 'scan' all object keys within a config file object. Which results in unwanted methods being added to the helpers object

We need to make a decision on how to keep the existing functionality and avoid this outcome. First seen here #69 #71

Replication/Example