added fix-indent command

Re-indents the eval_string, useful for amend_line and play, etc

lib/pry/commands/fix_indent.rb

@@ -0,0 +1,19 @@
+class Pry
+  class Command::FixIndent < Pry::ClassCommand
+    match 'fix-indent'
+    group 'Input and Output'
+
+    description "Correct the indentation for contents of the input buffer"
+
+    banner <<-USAGE
+      Usage: fix-indent
+    USAGE
+
+    def process
+      indented_str = Pry::Indent.indent(eval_string)
+      eval_string.replace indented_str
+    end
+  end
+
+  Pry::Commands.add_command(Pry::Command::FixIndent)
+end