Modify file type

- 755 -> 644
Add gem for testing as a development dependency
Fix to use 'documentation' formatter

'specdoc' is not defined.
Add missing `require`

newgem spec should require 'spec_helper'.
Merge pull request #2254 from tricknotes/644

Modify file type
Merge pull request #2255 from tricknotes/fix-gem-template

Fix gem template
reference the source priority section

[ci skip]