Shellquote arguments to `honcho run`

Again emulating Foreman behaviour, this patch quotes incoming arguments to
honcho run, which makes it possible to pass in arguments with spaces:

    honcho run git commit -m "hello world"

N.B. This does break compatibility with honcho 0.2.0, as it means that
arguments will no longer be interpolated in the shell. In honcho 0.2.0:

    $ NAME=world honcho run echo 'Hello $NAME'
    Hello world

Now:

    $ NAME=world honcho run echo 'Hello $NAME'
    Hello $NAME
Merge pull request #25 from mgax/run-args

Shellquote arguments to `honcho run`
Replace README.md with README.rst
Bump version -> v0.3.0
Fix setup.py
Bump version -> v0.3.1
Merge remote-tracking branch 'honcho/master' from nick into win_support

Conflicts resolved for:
	honcho/__init__.py
	test/integration/test_env.py