Fix paths in pkg-config file

Update build system and continuous integration

feat: update bmi.h functions to pass pointers to Bmi struct (#5)

* update bmi.h for the initialize function of bmi 2.0

* rename BMI_Model to Bmi

Update bindings to BMI v2.0

Beta 0 release for BMI v2.0

Add BMI_Get_var_itemsize function

It was mistakenly omitted. This fixes #1.