add Windows testing

[mschilli87]

new version of #43 targeting dev2 branch which is identical to dev except for the unintended merge.

[mschilli87]

@retaj:

I gave this another quick try and currently R CMD INSTALL fails on windows with

* installing *source* package 'ciRcus' ...
** R
** inst
** preparing package for lazy loading
Error in loadNamespace(i, c(lib.loc, .libPaths()), versionCheck = vI[[i]]) :
  there is no package called 'GenomeInfoDbData'
ERROR: lazy loading failed for package 'ciRcus'
* removing 'C:/projects/circus/ciRcus.Rcheck/ciRcus'
In R CMD INSTALL

This was on 32bit R 3.4.4 in case it matters.

[mschilli87]

rebased on latest dev

---

edit: same old story:

* installing *source* package 'ciRcus' ...
** R
** inst
** byte-compile and prepare package for lazy loading
Error in loadNamespace(i, c(lib.loc, .libPaths()), versionCheck = vI[[i]]) :
  there is no package called 'GenomeInfoDbData'
ERROR: lazy loading failed for package 'ciRcus'
* removing 'C:/projects/circus/ciRcus.Rcheck/ciRcus'
In R CMD INSTALL