Merge pull request #2 from fcavalcanti/master

Pull IR calibration data.
Performed third-order polynomial linear regression on IR calibration data.
Added a conclusion to `calibration_data.md`.
Replaced the implementation of `IR_conv()` with the method described in `calibra
tion_data.md`. Gave `IR_calibrate` the `save_means` argument.
Initial SONAR lab commit.
Fixed type of `IR_conv()`, and finished `IR_lab.c`
Implemented `sonar_init()`.
Merge pull request #3 from dwtj/master

Lab 07