Use upstream ruby-magic project

The upstream version has all the changes in ruby-magic-static, as well
as an additional fix (https://github.com/kwilczynski/ruby-magic/pull/2).

Gemfile

@@ -274,7 +274,7 @@ gem 'licensee', '~> 9.14.1'
 gem 'charlock_holmes', '~> 0.7.7'
 
 # Detect mime content type from content
-gem 'ruby-magic-static'
+gem 'ruby-magic', '~> 0.3'
 
 # Faster blank
 gem 'fast_blank'

Gemfile.lock

@@ -1109,7 +1109,7 @@ GEM
       i18n
     ruby-fogbugz (0.2.1)
       crack (~> 0.4)
-    ruby-magic-static (0.3.1)
+    ruby-magic (0.3.0)
     ruby-prof (1.3.1)
     ruby-progressbar (1.11.0)
     ruby-saml (1.7.2)
@@ -1555,7 +1555,7 @@ DEPENDENCIES
   rspec_junit_formatter
   rspec_profiling (~> 0.0.6)
   ruby-fogbugz (~> 0.2.1)
-  ruby-magic-static
+  ruby-magic (~> 0.3)
   ruby-prof (~> 1.3.0)
   ruby-progressbar (~> 1.10)
   ruby_parser (~> 3.15)