Merge pull request #34 from kallelampila/master

return error code on exit status, if build failed
Fixed build step stalling on Ubuntu 14.10

Ubuntu 14.10 includes an updated bash version which apparently includes
stricter parsing which resulted in buildgear stalling in the build step.
Update buildgear.org to buildgear.io

Since http://buildgear.io is the new home of Build Gear all references
have been updated accordingly.
Add existing file size for resumed downloads

We want to show the user the progress of the entire file download,
not just the part downloading in this session.
Sort manifest lists alphabetically

To give a better overview the manifests lists are now sorted by build
name in alphabetical order.
Merge branch 'master' of github.com:buildgear/buildgear
Bumped version
Updated ChangeLog
Added sensible chapter id
Resolve source_dir (SOURCE) path

The 'source_dir' path was not being resolved which resulted in $SOURCE
being non-resolved.

This had the unfortunate effect that builds like crosstool-ng would not
find the $SOURCE path nor any previously downloaded source. Subsequently
it would download sources from scratch at every rebuild slowing down the
build.
Optimized 'show --buildfile' command

Optimized the 'show --buildfile' command to avoid the use of temporary
files in /tmp and reduce the number of calls to external programs.
Renamed .buildgear/.lock to .buildgear/lock

No need to make the lock file hidden since it is already in a hidden
directory.
Add rebuild detection based on buildfile checksum

This means that a build will automatically rebuild if the sha256sum
checksum of its bash expanded Buildfile changes.

This is particular useful if you use configurations variables to
reconfigure the way your firmware is built.

For example, if you have a configuration variable in the global
buildfiles configuration file (config/config), eg.:

CONFIG_AUDIO="alsa"

And in one or more Buildfiles you use this variable to reconfigure the
build or change dependencies. For example:

if [ "$CONFIG_AUDIO" == "alsa" ]
then
   CONF_OPTIONS+="--audio=alsa"
   depends+=(alsa-lib)
else
   CONF_OPTIONS+="--audio=oss"
fi

Now, if you change the value of CONFIG_AUDIO between builds, then build
gear will automatically rebuild any buildfiles that uses CONFIG_AUDIO
because it will detect that the the checksum of the bash expanded
buildfile(s) changes by this modification.
Bumped version
Fixed layer name output padding
Support builds with no package output

This feature adds support for buildfiles which include a build()
function but produces no package output (no files installed in $PKG).
Updated handbook
Merge branch 'support_no_package_output'
Updated ChangeLog
Do not expand ` calls for buildfile checksums