Documentation install optional uses '.[dev]' syntax, but windows syntax is .[dev]

[JoeZiminski]

Results in the following error running Windows 10 in Pycharm (pip install):

(test_brainreg_dev) C:\fMRIData\git-repo\brainreg>pip install -e '.[dev]' ERROR: '.[dev]' is not a valid editable requirement. It should either be a path to a local project or a VCS URL (beginning with bzr+http, bzr+https, bzr+ssh, bzr+sftp, bzr+ftp, bzr+lp, bzr+f ile, git+http, git+https, git+ssh, git+git, git+file, hg+file, hg+http, hg+https, hg+ssh, hg+static-http, svn+ssh, svn+http, svn+https, svn+svn, svn+file).

We could update documentation to cover both cases