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Composer require, no colon when using command line [1]

[1] http://getcomposer.org/doc/03-cli.md#require
Merge pull request #72 from SemanticMediaWiki/install

Improve INSTALL instructions
Update INSTALL.md

typos and tweaks
Merge pull request #77 from kghbln/master

Update INSTALL.md
Merge branch 'master' of ssh://review/mediawiki/extensions/SemanticMediaWiki