Added ability to set context in charts.yaml (#21)

* Added ability to set context in charts.yaml

* Added context to the documentation
Added error if —kube-context and context are both used.

state/state.go

@@ -20,6 +20,7 @@ import (
 
 type HelmState struct {
 	BaseChartPath string
+	Context       string           `yaml:"context"`
 	Repositories  []RepositorySpec `yaml:"repositories"`
 	Charts        []ChartSpec      `yaml:"charts"`
 }