Use format as default format

Use format form options as format if the format cannot be infered from the filename.
Update Controller/ImagineController.php

Set format to null if not defined by the options.
Merge pull request #76 from tarjei/patch-1

Use format as default format
fix typo on adding options when saving
Merge pull request #84 from Sewdn/master

fix typo when adding options for saving image
Add content-length Header
Header content length without file access
Update to composer
Merge pull request #90 from xavren/develop

Add content-length Header
Merge pull request #92 from armetiz/patch-1

Update to composer
fix typo
Update composer.json

Updated version requirements
Update composer.json

added repository for imagine/imagine
Update README.md

updated install documentation
Merge pull request #97 from butt/develop

Updated composer workflow
Merge branch 'develop'

Conflicts:
	Controller/ImagineController.php
fix imagine version
fix Imagine version
revert multiple filters feature
Added cache manager.
Fixes #96.