* Declare ShellConfig.execPath property
See its usage in
https://github.com/shelljs/shelljs/blob/master/src/exec.js
* [shelljs] Add tslint.json
The tslint.json config includes two exceptions:
- unified-signatures = false because overloaded methods have different
enough purposes to warrant a separate documentation
- max-line-length = false because existing documentation breaks the
rule, and it seems better fixed separately
Code changes are straightforward style changes suggested by the linter.