Small typo fixes + unsafe string comparison fix

doc/tutorial/debug_faq.txt

@@ -288,12 +288,12 @@ can be achieved as follows:
 
 To help understand what is happening in your graph, you can
 disable the ``local_elemwise_fusion`` and all ``inplace``
-optimizations. The first is a speed optimization that merge elemwise
-operations together. This make it harder to know which particular
-elemwise cause the problem. The second optimization make some ops
-output overwrite its input. So, if an op create a bad output, you
-won't be able see the input that was overwriten in the ``post_fun``
-function. To disable those optimization (with a Theano version after
+optimizations. The first is a speed optimization that merges elemwise
+operations together. This makes it harder to know which particular
+elemwise causes the problem. The second optimization makes some ops'
+outputs overwrite their inputs. So, if an op creates a bad output, you
+will not be able to see the input that was overwriten in the ``post_func``
+function. To disable those optimizations (with a Theano version after
 0.6rc3), define the MonitorMode like this:
 
 .. code-block:: python
@@ -311,7 +311,7 @@ function. To disable those optimization (with a Theano version after
     mode with MonitorMode, as you need to define what you monitor.
 
 To be sure all inputs of the node are available during the call to
-``post_func``, you also must disable the garbage collector. Otherwise,
+``post_func``, you must also disable the garbage collector. Otherwise,
 the execution of the node can garbage collect its inputs that aren't
 needed anymore by the Theano function. This can be done with the Theano
 flag:

theano/compile/monitormode.py

@@ -37,14 +37,14 @@ class MonitorMode(Mode):
         :param optimizer: The optimizer to use. One may use for instance
             'fast_compile' to skip optimizations.
 
-        :param linker: DO NOT USE. This mode use its own linker.
+        :param linker: DO NOT USE. This mode uses its own linker.
             The parameter is needed to allow selecting optimizers to use.
         """
         self.pre_func = pre_func
         self.post_func = post_func
         wrap_linker = theano.gof.WrapLinkerMany([theano.gof.OpWiseCLinker()],
                                                 [self.eval])
-        if optimizer is 'default':
+        if optimizer == 'default':
             optimizer = theano.config.optimizer
         if (linker is not None and
             not isinstance(linker.mode, MonitorMode)):

theano/compile/pfunc.py

@@ -442,7 +442,8 @@ def pfunc(params, outputs=None, mode=None, updates=None, givens=None,
     if len(updates) > 0 and any(isinstance(v, Variable)
                                 for v in iter_over_pairs(updates)):
         raise ValueError(
-            "The updates parameter must an OrderedDict/dict or a list of list/tuple with 2 elements")
+            "The updates parameter must be an OrderedDict/dict or a list of "
+            "lists/tuples with 2 elements")
 
     # transform params into theano.compile.In objects.
     inputs = [_pfunc_param_to_in(p, allow_downcast=allow_input_downcast)