Deleted copy of readme.md in ./src/main/java/tfm

Also optimized imports

* Adds API `asXArc` and `isXArc` to Arc.
* Adds Sliceable interface for graphs.
* Removed old DOT methods (toGraphvizRepresentation)
* Removed representation-related methods from graphs.
* Removed unnecessary methods.

Each method is graphed, and then all possible slices are compared.

Renamed graphs to remove redundant `Graph` at end of class names.

API changed from returning a graph to returning a set of `GraphNode#id`s.

Includes documentation for the updated classes.

Covers statements, loops, `if`, `switch`, jumps (`break`, `return`...).
Does not include elements from the ACFG.

Fixes #8