refactor(datastore/fetch): Makes more failure proof fetching user-data files

- Adds URL validations
- Adds timeout support for http client
- Limits the amount of retries to not spin forever
- Fails faster if response status code is 4xx
- Does a little bit more of logging
- Adds more tests
style(datastore/fetch): Adjusts comments formatting
fix(datastore/fetch): off-by-one oversight
fix(docs): add documentation for fleet section
Response body must not be closed if request error'd.
Merge pull request #115 from burke/master

Response body must not be closed if request error'd.
Merge pull request #109 from jonboulle/fleet

fix(docs): add documentation for fleet section
test(datastore/fetch): Makes sure err is not nil
Merge pull request #114 from c4milo/fetch-url-refactor

refactor(datastore/fetch): Makes more failure proof fetching user-data files.
chore(travis): Adds travis yaml file and badge in README
Merge pull request #117 from c4milo/travis-support

chore(travis): Adds travis yaml file as well as badge in README
chore(logging): Removes duplicated timestamp during booting
chore(coreos-cloudinit): bump to 0.7.0
chore(coreos-cloudinit): bump to 0.7.0+git
feat(units): Add generic cloudinit path unit

Switch to triggering common user configs via a path unit. This is
particularly useful for config drive so that a config drive can be
mounted by something other than the udev triggered services, a bind
mount when running in a container for example.
fix(etcd): fix runtime panic when etcd section is missing.

The etcd code tries to assign ee["name"] even when the map was never
defined and assigning to an uninitialized map causes a panic.
Merge pull request #119 from marineam/container

container and panic fixes
chore(coreos-cloudinit): bump to 0.7.1
chore(coreos-cloudinit): bump to 0.7.1+git
Merge pull request #118 from c4milo/log-timestamp-fix

chore(logging): Removes duplicated timestamp during booting