Typo in usage.rst
Spelling and grammar corrections in the provided examples
Rename National Instrument to National Instruments in citation
Spelling and grammar corrections in the documentation
Use "note" admonition directive for open source driver note
Cleanup sh code-block directive
Use code-block directive for C code blocks for syntax highlighting
Perform boolean testing on taskHandle and not taskHandle.value

If `DAQmx_copyright_year >= 2010`, taskHandle no longer has type c_int
but c_void_p. The problem is that `c_void_p(0).value != 0` since
`c_void_p(0).value` returns None.

Also fix a related bug where `'%d' % taskHandle.value` raises TypeError
by first checking for a valid task before formatting repr string.
Add some sensible flags to the numpy ndpointer type-checking instance
Fix example code, callbacks should return an integer
Retab mixed tabs and spaces
Use 4 spaces for indentation
Update path for NI Acq-IntClk.c example

This is the new path as of at least NI-DAQmx 9.9.5 (July 2012).
Use inline markup where applicable
General improvements to the content and formatting of the documentation
Mention pip as a possible installation method
Include error handling in Python version of Acq-IntClk.c

This more accurately reflects real-world usage, and more accurately
mirrors the C example.

A final note is included mentioning that cleanup is not necessary if
using the object-oriented interface.
Automatically add horizontal scrollbars to overflowing code blocks
Add example of how to synchronise threads with callbacks

This example shows how to synchronise a main thread with the
asynchronously-called EveryNSamplesEventCallback, using the
object-oriented Task interface.
Use `os.path.join()` instead of string concatenation for file paths