Unable to install from github with devtools or githubinstall

When trying to install the latest version of ggmap from github using devtools or githubinstall, it fails with this error:

```r
> devtools::install_github("dkahle/ggmap")
Downloading GitHub repo dkahle/ggmap@master
from URL https://api.github.com/repos/dkahle/ggmap/zipball/master
Installing ggmap
"C:/PROGRA~1/Microsoft/R Client/R_SERVER/bin/x64/R" --no-site-file --no-environ --no-save --no-restore --quiet CMD INSTALL \
"C:/Users/ChrisMartin/AppData/Local/Temp/RtmpQDXW48/devtools807425096b3e/dkahle-ggmap-8365275" --library="D:/Downloads/R/win-library/3.3" --install-tests

'C:\PROGRA~1\Microsoft\R' is not recognized as an internal or external command,
operable program or batch file.
Error: Command failed (1)
```

Similar with githubinstall.