Add curl example for container linking
[origin_cartridge_200]Met "panic: runtime error: invalid memory address
or nil pointer dereference" when sti/gear build with -s option

https://bugzilla.redhat.com/show_bug.cgi?id=1105469
Merge pull request #236 from bparees/handle_invalid_url

[origin_cartridge_200]Met "panic: runtime error: invalid memory address or nil pointer dereference" when sti/gear build with -s option
Merge pull request #234 from vnugent/master

Add curl example for container linking
gear build generate new image when do incremental build

https://bugzilla.redhat.com/show_bug.cgi?id=1118231
Merge pull request #239 from bparees/support_remove_old_image

gear build generate new image when do incremental build
Bug 1118122 - Allow overriding the git based version string with ENV var
Merge pull request #238 from mfojtik/version_str

Bug 1118122 - Allow overriding the git based version string with ENV var