`git pull` args re-ordering

Previous implementation could produce: `git pull origin master --rebase`, which results in an error. `git pull --rebase origin master` is correct.
Merge pull request #9 from joeybaker/patch-1

`git pull` args re-ordering
Update readme to reflect callbacks

It's very likely, these commands will need to happen serially, therefore, it's important to ensure that gulp knows to wait for task completion before proceeding. This clarifies the docs to show that commands accept a callback or are part of a stream.
Only some examples need to show callbacks

Per https://github.com/stevelacy/gulp-git/pull/10#issuecomment-36665234
Fix typo
Merge pull request #11 from joeybaker/patch-2

Fix missing default args in push
Merge pull request #10 from joeybaker/patch-1

Update readme to reflect callbacks
Whitespace cleanup
Add jshint and jscs