Minor fixes (#613)

* Minor doc syntax fix

The numpy documentation had a bad :file: reference (was using double
backticks instead of single backticks).

* Changed long-outdated "example" -> "tests" wording

The ConstructorStats internal docs still had "from example import", and
the main testing cpp file still used "example" in the module
description.

docs/advanced/pycpp/numpy.rst

@@ -155,7 +155,7 @@ NumPy array containing double precision values.
 When it is invoked with a different type (e.g. an integer or a list of
 integers), the binding code will attempt to cast the input into a NumPy array
 of the requested type. Note that this feature requires the
-:file:``pybind11/numpy.h`` header to be included.
+:file:`pybind11/numpy.h` header to be included.
 
 Data in NumPy arrays is not guaranteed to packed in a dense manner;
 furthermore, entries can be separated by arbitrary column and row strides.

tests/constructor_stats.h

@@ -24,7 +24,7 @@ function calls to constructors:
         ...
     }
 
-You can find various examples of these in several of the existing example .cpp files.  (Of course
+You can find various examples of these in several of the existing testing .cpp files.  (Of course
 you don't need to add any of the above constructors/operators that you don't actually have, except
 for the destructor).
 
@@ -41,7 +41,7 @@ value constructor) for all of the above methods which will be included in the ou
 For testing, each of these also keeps track the created instances and allows you to check how many
 of the various constructors have been invoked from the Python side via code such as:
 
-    from example import ConstructorStats
+    from pybind11_tests import ConstructorStats
     cstats = ConstructorStats.get(MyClass)
     print(cstats.alive())
     print(cstats.default_constructions)

tests/pybind11_tests.cpp

@@ -32,7 +32,7 @@ void bind_ConstructorStats(py::module &m) {
 }
 
 PYBIND11_PLUGIN(pybind11_tests) {
-    py::module m("pybind11_tests", "pybind example plugin");
+    py::module m("pybind11_tests", "pybind testing plugin");
 
     bind_ConstructorStats(m);