Improving the performance of MIME::Types#type_for

- The performance improvement is about 20–25%.
Unsort extensions, restore old sort order.

Resolves #71.
Adding MIME::Type#friendly.
Adding reg, ps1, and vbs extensions.

Fix #69.
Documenting convert methods in support.
Increasing robustness of MIME updating.
Updated IANA type definitions.
Finalizing mime-types 2.4 release.
Added mime type for MS Outlook application

Added content type ‘application/vnd.ms-outlook’ for the application MS
Outlook with the file extension ‘.msg’. This is not registered in IANA
but found the content type at
http://www.digitalpreservation.gov/formats/fdd/fdd000379.shtml.

Made changes to avoid failure on travis

Reverted back the changes
Finalized 2.4 release with JSON conversion.