README fixes. No functional changes.

  * Converted to Markdown.
  * Organization fix: Instructions on how to get the source come
    first.
  * Fixed old Google code URL to point to github instead.
  * Grammar fixes.
  * Added examples.
Merge pull request #1 from wiseman/fixreadme

README fixes. No functional changes.
AP_Param: removed copy_name() and add token to find_by_index()

this allows callers to avoid another var_info traverse
Rover: update for new AP_Param API
Plane: update for new AP_Param API
Copter: update for new AP_Param API
MAVLink: cope with available() returning -1
autotest: use mktemp instead of tempfile

more portable
autotest: fixed jsbsim on fedora
autotest: ensure JSBSim is dead on restart
AP_Baro: skip timer if we don't get the SPI semaphore
AP_InertialSensor: ensure we always have the SPI semaphore for MPU6k
AP_InertialSensor: poll for new data in num_samples_available()

this lowers the latency for new data
HAL_AVR: make _taken volatile
AP_HAL: added WARN_IF_UNUSED macro

useful for key functions
AP_HAL: mark semaphore take operations as WARN_IF_UNUSED

this prevents common bugs
AP_Compass: ensure we check we got the semaphore
AP_Baro: added accumulate() function

this allows us to read the BMP085 much faster
AP_Baro: update example to use accumulate()
Copter: check bitmask in more logging functions