Make Build.settings a cached_property

This will cache the property as long as the instance of the build object
lives, which will give one read of the yaml file instead of three during
Build.run_test().
Merge pull request #28 from tind/cached-settings

Make Build.settings a cached_property
Limit list of builds to 100 elements, (closes #25)
Merge pull request #32 from tind/limitresults

Limit list of builds to 100 elements, (closes #25)
Added Gitter badge
Merge pull request #34 from gitter-badger/gitter-badge

Add a Gitter chat badge to README.md
Simplifu _run_task by removing double run
Merge pull request #38 from tind/issue37-remove-script-run-task

Simplify _run_task by removing double run
Fix syntax error in run_task
Captues the output from _run_task and saves it in result object
Add Project model and automatically create projects

related to #24
Move BuildResult below Build
add Project in admin
fix small issues with new Project model #24
Move all github related code into helpers.github
Remove test of code that is removed
Add tests for Project model
Move start build to project model
fix generation of github url
Add github helper to generate pull request url