fix(Gruntfile): Add relative paths to shell commands

For users without `./node_modules/.bin` in their shell path.
fix(resolveRequire): Normalize paths, simplify regex

- Refactor conditionals into positive checks
- Simplify regex by using presence checks only
- Now that Windows absolute paths are normalized before regex test,
  omit forward slash as acceptable character
- Detect relative paths based on a leading dot because the subsequent
  slash (either type) will be stripped by normalization anyway
- When returning paths, always normalize them (ex. Windows user tries
  to use non-NT-style)
docs(changelog): Add 0.3.5 note