Adding tests for fundamental and a test-generator executable

This PR does a few significant things:
- Adds an executable `hindent-generate-tests` which can "port" tests from one style to another. Namely, it looks in the test directory in the source style, and for each test case in that directory, generates a test file and expectation file for the destination style.
- I ran `cabal run hindent-generate-tests gibiansky fundamental` to create the `fundamental` style test cases.
- Added the `fundamental` style to the test cases and verified that it generates the right things (the fundamental style passes tests).

This PR is a prerequisite for further work on #9, which is more or less done but I need to verify that it hasn't changed behaviour for the `fundamental` style (`gibiansky` style passes all tests already).