Initial EDF class to load headers and signals into Ruby objects

`edfize` command has the following actions:

- `check`: Validates EDFs in the current directory for errors
- `test`: Same as `check`
- `run`: Prints out the headers of all edfs in the current directory
- `help`: Displays information about `edfize` along with all available commands
- `version`: Displays the current `edfize` version