v0.2.0

QuantumESPRESSOFormatter v0.2.0

Diff since v0.1.2

Merged pull requests:

• New version: v0.1.2 (#18) (@singularitti)
• Deprecate the FormatConfig will cause StackOverflowError (#19) (@singularitti)
• Deprecate _asstring since we have Iterators.map (#20) (@singularitti)