pkgenv command to edit package set environments. Fixes #41.
Merge pull request #42 from eaigner/master

pkgenv command to edit package set environments. Fixes #41.
add zsh install support
Merge pull request #44 from wting/add_zsh_install_support

Add zsh install support
Added build-essential to the Linux requirements

Without this instruction change, people might come across a "`unistd.h` not found" error.
Make gvm pkgenv sensitive to the EDITOR environment variable

For those who do not use 'vi', although 'vi' is still the default.
Use "$PATH" to avoid weirdness.

Without this, I get this error when gvm is being loaded:

    /home/manveru/.gvm/scripts/gvm-default:export:17: not an identifier: 2:/home/manveru/node_modules/.bin:/home/manveru/github/akunspy/gopbuf/bin:./node_modules/.bin:.
Merge pull request #52 from manveru/patch-1

Use "$PATH" to avoid weirdness.
Merge pull request #51 from fdr/editor

Make gvm pkgenv sensitive to the EDITOR environment variable
add output option to pkgenv

Using `pkgenv -o` or `pkgenv --output` will now cat the file instead of editing it.
Update gvm-installer

Add some description for "profile settings file"
Merge pull request #55 from zhibinr/patch-1

Update gvm-installer
Merge pull request #54 from extraordinaire/master

add output option to pkgenv
Merge pull request #47 from shovon/master

Added build-essential to the Linux requirements
* Use $(..) instead of deprecated `..`, which can produce unknown behaviors on posix systems
* No need to change path when git cloning - use --quiet instead of redirecting stdout
* $GVM_ROOT is the variable content, not the variable itself - better display GVM_ROOT to the user than $GVM_ROOT
* When executing $GVM_ROOT/scripts/$command - args need to be quoted otherwise they are treated as $*, which will break on spaces
* Proper use of printf
* Prevent possible word splitting when eval sudo
* Best practice, to avoid possible break on space as in $*
Linux distro specificities
Merge pull request #56 from alouche/master

Linux distributions specific + minor shell safety belts