Changes in version 0.4.2
 * Load XLSX files as data.table instead of data.frame
Changes in version 0.4.1
 * Bringing tstools back to CRAN, maintenance release.
Changes in version 0.3.6.1
 * regularize series using NAs, better plot support for NAs, smaller bugfixes
Changes in version 0.3.6
 * major co-ordination fixes, auto legends fixes. enjoy!
Changes in version 0.3.5.1
 * CRAN release
Changes in version 0.3.4.2
 * Improvement of tick handling, more automatic determination
Changes in version 0.3.4
 * introduced data.table dependency
Changes in version 0.3.3
 * speedup writeTimeSeries by optionally using data.table's rbindlist
Changes in version 0.3.2
 * optional data.table read csv for speedup
Changes in version 0.3.1
 * minor add ons, problems in versions fixed
Changes in version 0.3
 * function to create regular time series from data.frames
Changes in version 0.2.7.9.1
 * minor change to unit test to avoid re-import warning with other packages that load openxlsx.
Changes in version 0.2.7.9
 * added function to turn quarterly to monthly series (interpolate).
Changes in version 0.2.7.8
 * added function to start after last internal NA.
