Use specific versions for package depedencies

[itziakos]

It looks that we are currently running tests using the latest master version of the simphony-commons library. As a result due to frequent changes (some of the not backwards compatible) that take place in the simphony-commons library will cause the test builds to fail, which make developement a litle more complicated.

To counter the effects of a fast paced development in simphony-common a common pattern is to

• First always use a fixed version for the depedencies in requirements files so that there is always control on what we are testing again.
• Setup a second build configuration that will run tests against the latest master version of simphony-commons to see possible issues if we had upgraded to the latest version but does not cause the travis-ci check to failure.

@khiltunen, if it ok with you, I can update the travis-yml configuration with the above pattern. It would be a good example to the other simphony collaborators on how to use travis-ci to better manage depedenvy issues with new versions of simphony-common

[khiltunen]

This is ok

[jmarcelogimenez]

Is this issue solved by #19 ?

[nathanfranklin]

Yea, this issue is addressed by #19 (but needs to be updated to reflect changes in master and that simphony-common 0.1.3 is the stable release being used)