Update mobile-services-android-call-custom-api.md

ApiOperationCallback needs to be included or the steps in this guide will fail on ADT 20131030 with Java 1.6 and API 18
Mobile Services: Adding call-custom-api-html and a reference to it in get-started-html
Changing reference to pip2.7 command
Merge pull request #2875 from WindowsAzure/AUX431

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Merge pull request #2893 from WindowsAzure/AUX431

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Merge pull request #2905 from WindowsAzure/AUX431

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Merge pull request #2925 from WindowsAzure/AUX431

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Merge pull request #2935 from WindowsAzure/AUX431

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fixed broken links in two topics
Merge pull request #2954 from Justinha/04142014Working

fixed broken links in two topics
Merge pull request #2960 from WindowsAzure/AUX431

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initial refactor
Merge branch 'AUX431' of github.com:WindowsAzure/azure-content-pr into refactorcapistrano
added links
Merge pull request #2979 from WindowsAzure/AUX431

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Merge pull request #2971 from Justinha/04162014Working

added links
Merge branch 'AUX431' of github.com:WindowsAzure/azure-content-pr into refactorcapistrano
Merge pull request #3037 from WindowsAzure/AUX432

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refactoring
refactoring