clinPK 0.11.1

Major changes

• various corrections in nca() function
• various updates to AKI staging equations: MDRD equation (use 2006 publication), kDIGO and PRIFLE
• added equations of MDRD and CKD-EPI without race

Minor updates

• refactor of calc_ibw()
• fixed Boyd equation in calc_bsa()
• added function to convert flow units
• updates to 2-sample equation
• added Cockcroft-Gault equation for spinal cord injury patients
• consistent handling of missing/unrecognized data in calc_ibw()/calc_ffm()/calc_egfr()
• various minor fixes and updates
• various documentation updates
• added many unit tests, increase overall coverage to >86%