7 add persistance specs

Issue #7 

Summary
---
* Added specs covering `.save` and `.load`
* Changed the stream writing to use `print` instead `puts`
* Added support for `guard-rspec`

Specs
---
```
Finished in 1.15 seconds
16 examples, 0 failures
```

Documentation
---
```
Files:           8
Modules:         3 (    0 undocumented)
Classes:         4 (    0 undocumented)
Constants:       7 (    0 undocumented)
Methods:        16 (    0 undocumented)
 100.00% documented
```