fix to sharejs version

Missing hyphen fixes this issue:

npm http 200 https://registry.npmjs.org/share
npm ERR! Error: No compatible version found: share@'>=0.7.0alpha3 <0.8.0-'
npm ERR! Valid install targets:
npm ERR! ["0.1.0","0.1.1","0.2.1","0.2.2","0.3.0","0.4.0","0.4.1","0.5.0-pre","0.5.0","0.6.0","0.6.3","0.6.2","0.7.0-alpha","0.7.0-alpha2","0.7.0-alpha3","0.7.0-alpha4","0.7.0-alpha5","0.7.0-alpha6","0.7.0-alpha7"]
Merge pull request #4 from aogriffiths/patch-1

fix to sharejs version