Merge pull request #47 from hafen/dev

PR
Merge pull request #48 from hafen/dev

Fix travis.yml to install suggested package
Merge pull request #49 from hafen/dev

Better rCharts support
Merge pull request #50 from hafen/dev

PR
Merge pull request #53 from hafen/dev

Dev
Merge pull request #54 from tesseradata/dev

Dev
Merge pull request #55 from hafen/dev

Dev
Merge pull request #56 from tesseradata/dev

Dev
Merge pull request #58 from hafen/dev

Dev
Merge pull request #59 from tesseradata/dev

Dev
Merge pull request #60 from hafen/dev

Dev
Merge pull request #61 from tesseradata/dev

Dev
avoid deprecated usage of devtools installer

`devtools::install_github(repo, user)` is deprecated.
Merge pull request #64 from renkun-ken/patch-1

Avoid deprecated usage of devtools installer
Merge remote-tracking branch 'upstream/master' into dev