Fix typo in docstring.

Cython/Compiler/Main.py

@@ -691,7 +691,7 @@ def compile(source, options = None, full_module_name = None, **kwds):
 
     Compile one or more Pyrex implementation files, with optional timestamp
     checking and recursing on dependencies.  The source argument may be a string
-    or a sequence of strings If it is a string and no recursion or timestamp
+    or a sequence of strings.  If it is a string and no recursion or timestamp
     checking is requested, a CompilationResult is returned, otherwise a
     CompilationResultSet is returned.
     """