readlines should be completable.

Fixes #921.

jedi/evaluate/compiled/fake/builtins.pym

@@ -32,9 +32,13 @@ def range(start, stop=None, step=1):
 class file():
     def __iter__(self):
         yield ''
+
     def next(self):
         return ''
 
+    def readlines(self):
+        return ['']
+
 
 class xrange():
     # Attention: this function doesn't exist in Py3k (there it is range).

jedi/evaluate/compiled/fake/io.pym

@@ -4,3 +4,6 @@ class TextIOWrapper():
 
     def __iter__(self):
         yield str()
+
+    def readlines(self):
+        return ['']

test/completion/stdlib.py

@@ -65,6 +65,11 @@ class X(): pass
 #? type
 type(X)
 
+
+with open('foo') as f:
+    for line in f.readlines():
+        #? str()
+        line
 # -----------------
 # enumerate
 # -----------------