* __init__.py now contains latest release version string
* installing from git checkout that does not correspond to a release commit
  will result in a more descriptive version string

setup.py now modifies __init__.py on build to include a more descriptive version string if .git is present.

New Profiler class from Antony Lee:
* Simpler API (with backward compatibility)
* Individual Profilers can be enabled by environmental variable PYQTGRAPHPROFILE

* Adjusted output formatting for clearer representation of nested profilers
* Message string formatting deferred until finish to reduce overhead

 * Loads only data that is currently visible
 * Downsamples to avoid plotting too many samples
 * Loads data in chunks to limit memory usage during downsampling

Added tools/setVersion script
setup.py now auto-generates version string based on pyqtgraph/__init__ and git info, if available

A new function profiling system is implemented.  Most importantly, this
allows one to profile various internal functions directly by setting the
`PYQTGRAPHPROFILE` environment variable to a comma separated list of
function and method names, e.g.

    PYQTGRAPHPROFILE=functions.makeARGB,ImageItem.render \
        python -mexamples

Specifically, items in `PYQTGRAPHPROFILE` must be of the form
`classname.methodname` or `dotted_module_name.functionname`, with the
initial "pyqtgraph." stripped from the dotted module name.

Moreover, the overhead of inactive profilers has been kept minimal: an
introspective check of the caller's name (only if `PYQTGRAPHPROFILE` is
set) and a trivial function (not method) call per profiler call.

The new profilers rely on `sys._getframe` to find the caller's name,
although the previous system (passing the caller's name explicitely)
could certainly have been kept instead.

Finally the API of profilers has been changed: register a
profiling point simply by calling the profiler, and profilers are
automatically flushed on garbage collection.  See the docstring of
`pyqtgraph.debug.Profiler` for more details.

- Speed improvements in functions.makeARGB
- ImageItem is faster by avoiding makeQImage(transpose=True)

- fixed makeARGB re-ordering of color channels

This allows ViewBox context menus to be modified by directly manipulating ViewBox.menu

The main change is on `ViewBox.getContextMenus`, which now returns an
up-to-date of actions that `GraphicsScene.addParentContextMenus` can use.

Also, `getContextMenus` was given a default implementation in the base
class (falling back on `getMenu` if defined), and some cleanup was done.

Extend ViewBox menu in examples/contextMenu

- Process now optionally wraps stdout/stderr from child process to
  circumvent a python bug
- Added windows error number for port-in-use check
- fixed segv caused by lost QImage input in pyside

This allows customization of the context menu of a ViewBox simply by
calling viewbox.menu.addAction(...).  See issue #13.  Also some cleanup.

 - Avoid using authkey on windows; seems to be broken
 - Included yet another method of accessing shared memory as QImage

Workaround is for ViewBox to see whether its scene has changed every time it paints.

Fixes: 12

Fixes #10

Faster import of PyQtGraph.