Assume that people use bundler

It's ubiquitous now.
Improve save_page for binary content
Merge pull request #1222 from joliss/readme

Assume that people use bundler
Merge pull request #1223 from cschramm/patch-1

Improve save_page for binary content
Run Travis tests on latest Chromedriver
Build on latest rbx version
Merge pull request #1240 from abotalov/use_rbx_on_travis

Use latest Chromedriver and rbx for Travis tests