Risu v1.5.0 Released

#1.5.0 (February 20, 2012)
- Updated the Item model to be compatible with Nessus 5.0
    - Added critical_risks()
    - Added critical_risks_unique()
    - Added critical to the Risks by Severity Graph
    - Everything that used High as its data now uses Critical
    - The new methods also have associated tests.
- Updated the Plugin model to be compatible with Nessus 5.0
    - Added critical_risks()
- Added New tags
    - Plugin Model
        - fname
    - Item Model
        - plugin_name (Not all plugins seem to support this XML struct yet)
- Added new Methods to the Reference class for accessing references easier
    - cve
    - cpe
    - cwe
    - iava
    - msft
    - osvdb
    - owasp
    - cert
    - edb_id
    - rhsa
    - secunia
    - suse
- Added new methods to the Item class
    - stigs_severity_graph()
    - stig_findings()
    - all_risks_unique_sorted() from [aeriff] on github
- New Templates
    - stig_findings_summary - Quick summary of all the stig related findings by severity
- Template Updates
    - technical_findings - Added critical risks
    - exec_summary - added critical risks and a stig graph
    - findings_host - added critical and lowered the font sizes a bunch
    - notable_detailed - added critical and changed header to Notable
    - exec_summary_detailed - added critical risks
    - host_summary - added critical risks
    - graphs - added stig graph
    - host_summary - added critical risks and page numbers
    - Misc changes in other templates
- Added test::unit tests for most of the specs