Changes 1.25.1
- fix user-supplied reference for PQN
- reset random seed state after knn

Changes 1.23.1
- fix broken test due to changes in RF imputation

Changes 1.15.1
- fix plots due to breaking changes in ggplot2

Changes 1.3.4
+ Added option to constrain spar values for QCRSC.

Changes 1.2.1 and 1.3.3
+ Account for missing injections in QCRSC.

Changes 1.3.2
+ Added inputs/outputs for pqn.
+ Fixed glog plot bug.

Changes 0.99.6
+ Updated vignettes.

Changes 0.99.2
+ Support for SummarizedExperiment class.
+ Updated documentation and vignette.
+ Added functions for QCRSC algorithm of signal-batch correction for MS data.

Changes 0.2.6
+ glog transformation can use fixed lambda value input.
+ Plot to visualise output of glog lambda value optimisation.

Changes 0.2.5
+ Pre-calculated  mean reference values can be used with PQN normalisation
    function.

Changes 0.2.4 (Release date: 2019-08-07)
+ Updated documetation and usage examples.
+ Refactored glog scaling function.
+ PQN normalisation supports using all samples to calculate correction factor.
