When testing if a blob is indexable, check size first

Otherwise, charlock_holmes will allocate another large binary
buffer for testing the encoding, which is a problem if the binary
blob is many hundreds of MB large. It'll just fail and crash ruby.

lib/linguist/blob_helper.rb

@@ -250,7 +250,9 @@ module Linguist
     #
     # Return true or false
     def indexable?
-      if binary?
+      if size > 100 * 1024
+        false
+      elsif binary?
         false
       elsif extname == '.txt'
         true
@@ -260,8 +262,6 @@ module Linguist
         false
       elsif generated?
         false
-      elsif size > 100 * 1024
-        false
       else
         true
       end