update readme for v0.2.0

- add sections for dependencies, installation, and testing.
- change branch in Travis CI url to v0.2.0 (not sure if that's how that works; we'll see)
git is not optional
Merge pull request #189 from jrperritt/v0.2.0

update readme for v0.2.0
Adding README for acceptance test directory
Adding "Download RC file" hint for OpenStack users
s/costsfrom/costs from
Moving compute resources into version dir
Minor fixes based on code review
Merge branch 'acceptance-test-readme' of github.com:jamiehannaford/gophercloud into acceptance-test-readme
Merge pull request #193 from jamiehannaford/compute-dir-restructure

Moving compute resources into version dir
Merge pull request #192 from jamiehannaford/acceptance-test-readme

Adding README for acceptance test directory
Merge remote-tracking branch 'upstream/v0.2.0' into identity-v3

Conflicts:
	acceptance/openstack/compute/tools_test.go