Added 'context' property for statuses
Fixed extra ')' in ChangeStatusUpdater.java
Update GitHubUsageStatisticsProvider.java

Fix character from russian 'с' to 'c'
Merge pull request #68 from VladRassokhin/patch-1

Update GitHubUsageStatisticsProvider.java
actuall nullability & backward compatibility case
allow nullables for context
add more tests. Revert older tests + left new tests
indenting
wording
add default value for new usages
optional field
Merge branch 'pull67'
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