v0.3.0-pre1

• add --volume-home option to use a Docker volume for homedir instead of host
  mount
• move ssh key into user image, so less set up required for homedir

$ sha1sum skeg_*
3cd54b0d08d3f231440e1f5f0fe4a353a2d9c908 skeg_darwin_amd64
929890f1e0dd0a48036adffb7f2d1a139fb6533b skeg_linux_amd64
ed1d1624903253c6823bcd782c39aaea60620603 skeg_windows_amd64.exe
$ sha256sum skeg_*
0b0f7db982244630242bb16883972e8f3b1ecbf098cbaee7d6546925961b09c3 skeg_darwin_amd64
d69b645d37ed4b5b4c0116bf567ceeae8b309ced93a560886fc45c7bb3b00d02 skeg_linux_amd64
b2dfbf8a12e24fc777d934de4572023bde8b5f2330fd4d3acf7a1f21bcbdf9c1 skeg_windows_amd64.exe
$ md5sum skeg_*
647084686007f472b91d7c3818191393 skeg_darwin_amd64
e8e983a5658f9e2a8dda56af2113756e skeg_linux_amd64
a5ed8e424b01e6b0921d4b8026c76a0a skeg_windows_amd64.exe