Update changelog.

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Add contributing instructions in the README.
Merge pull request #31 from ionia-corporation/update_changelog

Update the changelog.
Bump to version 0.5.0.
Fix when passing nil in a where condition.
Update CHANGELOG.md
New standard types added in new module.
Merge pull request #36 from ionia-corporation/standard_types

New standard types added in new module.
Don't append '__c' to default table name if SObject subclass is a namespaced standard type
Extract private method for selecting a table_name
Merge pull request #38 from DanOlson/namespaced-standard-type-table-name

Don't append '__c' to default table name if SObject subclass is a namesp...
Allow namespaced SObjects to declare associations without having to specify a foreign key
removed unnecessary include.
Merge pull request #40 from ionia-corporation/standard_types

removed awfully unnecessary include.
Extract association method for inferring a model's foreign key
Merge pull request #39 from DanOlson/namespaced-sobject-associations

Allow namespaced SObjects to declare associations without having to spec...
Support bind parameters
Merge pull request #42 from DanOlson/bind-parameters

Support bind parameters
Update changelog.
Merge callbacks branch.