Updating install documentation for composer

Composer.json files:
- Fixed composer example issues (Needs dev-stability to install)

Instantiating Sentry:
- Rearranged numbed explanation of objects in Sentry's parameter list
- Rearranged object instantiationto reflect Sentry params.
- Rearranged parameters in code example on Instantiating Sentry
Merge pull request #167 from thomaslarsson/master

Updating installation documentation for composer