Merge branch 'detect-prolog' of https://github.com/tautologico/linguist into tautologico-detect-prolog

Conflicts:
	lib/linguist/blob_helper.rb
	test/test_blob.rb

test/fixtures/test-perl.pl

@@ -0,0 +1,2 @@
+#!/usr/bin/perl
+print "Hello, world!\n";

test/fixtures/test-perl2.pl

@@ -0,0 +1,3 @@
+
+# Perl file without shebang
+print "Hello, world!\n";

test/fixtures/test-prolog.pl

@@ -0,0 +1,12 @@
+/* Prolog test file */
+male(john).
+male(peter).
+
+female(vick).
+female(christie).
+
+parents(john, peter, christie).
+parents(vick, peter, christie).
+
+/* X is a brother of Y */
+brother(X, Y) :- male(X), parents(X, F, M), parents(Y, F, M).