HRCalculations.R: Load IBI directly as vector instead of ASCII

[bastianilso]

Steffen had some code that can work with RHRV, loading directly the IBI as vector instead of loading it from a text file.

[SteffenLehmann]

Here is the code for loading a vector instead of making a new file:
Transforming the column into a time per beat
IBI_DF$beats = as.numeric(difftime(IBI_DF$Timestamp, IBI_DF$Timestamp[1] , units ="secs"))
Constructing the vector
IBI_Vector <- IBI_DF$beats
Loading the vector into the package loader
hrv.data = LoadBeatVector(hrv.data, IBI_Vector)