convert format to use regex replace for shebangs

indexOf will parse the entire string for `#1` while regex for beginning of string will fail-short if first chars don't match.

- Performance boost (more than 50% on large strings)
- Cleaner syntax
Extract shebang functions to external lib
apply project formating
SheBang -> Shebang
Merge pull request #88 from pgilad/origin/patch-1

refactor shebangs usage to helper lib
Cleaning up rewrite code to handle properties individually so we no longer need to whitelist node types
Excluding prefix from matching
Merge pull request #89 from jimfleming/rewrite_cleanup

Cleaning up rewrite code