Support fetch error code 500 (Server error)

DropBox API returns 500 errors rarely. 
For example, when the thumbnail of the broken picture is acquired etc.
Merge pull request #13 from nao-pon/500_error

Support fetch error code 500 (Server error)
Added composer config
Fixed syntax errors in composer.json file
Added root CA file to root of project
Added gitattributes file to excluded unneeded files from distribution
Updated composer.json with requires and suggests
Fixed require in composer.json
Fixed pear setup in composer.json
Updated release info for 0.5.2 release
1.0.0 release
Fix for dirname function returning "\"

For paths like "/myFile.txt" dirname returns "\" causing the API call to fail.
Merge pull request #14 from lucassp/master

Fix for dirname returning "\"
Update tests/setup

Change location of php binary in shebang
Merge pull request #15 from kachkaev/master

Fix location of PHP binary in tests/setup shebang