Fix Obj texture parsing error: where obj texture map statement contains texture option, it will fail to parse the correct image url, as a result, the texture won't be shown. Besides, we also add clamp texture mode for obj
Merge branch 'master' of git://git.autodesk.com/InfraWorks-OpenSource/assimp into zhanggo/FixObjtextureError
refactor the code, also  parse texture option explictly
Merge pull request #7 from zhgw01/zhanggo/FixObjtextureError

Fix obj texture parsing error when it contains texture option