add new test bag: phidgets_imu_upside_down

This is from a phidgets imu, running the phidgets_imu driver mounted on
a wheeled robot that drives a small trip through an office. The IMU is
mounted upside down (i.e., the chips on the board are on the upper side,
lin_acc.z is ~ -9.81). The USB port points to the right side of the
robot. Rotation quaternion from /base_link (x pointing forward, z
pointing up) to /imu is (0, 1, 0, 0).

Contains /imu/data_raw and /imu/mag topics.
first fixes
adapted to groovy
add new test bag: phidgets_imu_upside_down

This is from a phidgets imu, running the phidgets_imu driver mounted on
a wheeled robot that drives a small trip through an office. The IMU is
mounted upside down (i.e., the chips on the board are on the upper side,
lin_acc.z is ~ -9.81). The USB port points to the right side of the
robot. Rotation quaternion from /base_link (x pointing forward, z
pointing up) to /imu is (0, 1, 0, 0).

Contains /imu/data_raw and /imu/mag topics.
Merge pull request #8 from uos/master

added parameter: publish_tf
Merge pull request #12 from lorenzoriano/groovy into groovy
set "zeta" as a parameter for dynamic reconfigure in the .cfg file
Merge branch 'groovy' of https://github.com/mickeyxu/imu_tools into groovy
gyro drift correction function added in MARG implementation
Merge pull request #13 from mickeyxu/groovy

Added gyro drift correction part from Madgwick's report for the MARG implementation.
fix initialization of initial rotation

Thanks to PaulKemppi! Closes #4.