Switch GPX MIME type detection to use marcel

Gemfile

@@ -109,7 +109,7 @@ gem "logstasher"
 gem "bzip2-ffi"
 gem "ffi-libarchive"
 gem "gd2-ffij", ">= 0.4.0"
-gem "mimemagic"
+gem "marcel"
 
 # Used for browser detection
 gem "browser"

Gemfile.lock

@@ -259,9 +259,6 @@ GEM
     marcel (1.0.0)
     maxminddb (0.1.22)
     method_source (1.0.0)
-    mimemagic (0.4.3)
-      nokogiri (~> 1)
-      rake
     mini_magick (4.11.0)
     mini_mime (1.0.3)
     mini_portile2 (2.5.0)
@@ -512,8 +509,8 @@ DEPENDENCIES
   libxml-ruby (>= 2.0.5)
   listen
   logstasher
+  marcel
   maxminddb
-  mimemagic
   mini_magick
   minitest (~> 5.1)
   oauth-plugin (>= 0.5.1)

lib/gpx.rb

@@ -50,7 +50,7 @@ module GPX
       rescue Archive::Error
         io = ::File.open(@file)
 
-        case MimeMagic.by_magic(io)&.type
+        case Marcel::MimeType.for(io)
         when "application/gzip" then io = Zlib::GzipReader.open(@file)
         when "application/x-bzip" then io = Bzip2::FFI::Reader.open(@file)
         end