Add instruction for getting system info in Crosh.

Refer to the instruction given by @drinkcat in
https://github.com/drinkcat/chroagh/issues/54#issuecomment-58771224
Add instruction for getting system info in Crosh.

This time in the contributing section of Readme.

Refer to the instruction given by @drinkcat in
https://github.com/drinkcat/chroagh/issues/54#issuecomment-58771224
Reword 4bae48457043ebc8f420611311cb91a3844ec324
Move instruction for encrypting existing chroots
Add notice for avoiding perserving ownership issue

See issue #903
Update tip in Readme

Tell the users right away that they can disbale the proxy setting using -P
option. In case some users get panic, so they do not read the descriptions
carefully, when their proxies do not work and want to
disable them but just cannot find out how.
Add the type a usb/sd should be formatted for -m
fix errors
fix errors
Merge pull request #1231 from tonyxue/enchance-doc

Enchance documentations
Update CONTRIBUTORS
Clarify creating a chroot with a bootstrap tarball

Clarify that you also need to specify the `-t` parameter after downloading the bootstrap files.

Given that you don't get an error about missing a target when running `-f` without `-t`, it took me quite a while and some googling to figure out why the command in step 4 didn't work; given that it was in the readme and every other command before this didn't need additional parameters, it was surprising that I needed to also add the `-t` parameter. I kind of get the distinction between a bootstrap and a target now that I've done it but I think mentioning it will save someone else from having to figure out what they are doing wrong after literally following the steps in the readme.
Merge pull request #1243 from mixu/patch-1

Clarify creating a chroot with a bootstrap tarball
Merge remote-tracking branch 'upstream/master'