Update README.md

Author: afawcett

README.md

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 FinancialForce Apex Common
 ==========================
 
+[![Build Status](https://travis-ci.org/financialforcedev/fflib-apex-commons.svg)](https://travis-ci.org/financialforcedev/fflib-apex-commons)
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 **Dependencies:** Must deploy [ApexMocks](https://github.com/financialforcedev/fflib-apex-mocks) before deploying this library
 
 <a href="https://githubsfdeploy.herokuapp.com?owner=financialforcedev&repo=fflib-apex-common">