add .uploadFile command to be used by .element

handles fileUploads well
add `.chooseFile` method

.chooseFile(selector, localFile) will upload and select the file in the
provided selector given it is a select input.
TODO
add chooseFile method to readme
do not do doubleClick behind overlay on chrome or phantomjs
add phantomjs requirements for local testing
firefox does not supports doubleclick behind overlay either
process.exit(failures)
try to fix async test on travis-ci on phantom
move upload specs to desktop only
fix choosefile gif path due to new spec path
remove bad test: doubleClick behind overlay
Merge pull request #139 from camme/upload-file

add .chooseFile(selector, localFile, cb), .file() protocol, .uploadFile command