Merge pull request #14 from tspascoal/master

Add to commands help the missing description for vso help
updated version
corrected help text
updated version
Merge remote-tracking branch 'upstream/master'
Allow defining the API version on command by command  basis
  Allow the caller to define which API version it wants to use when a command is issued. If not specified use default API version
  Force default API version (if not caller not specified it) instead of relying on vso-client default API version
Improved vso assign command. Now allows assigning multiple workitems
Fix set repositories command