Allow struct fields be named as 'name' (issue #21)

[DmitrySamoylov]

Hey everyone!

To prevent clashing I extended names of internal mut variables used for field initialization

For example after cargo expand:
Before (was clashing with XmlNode::SomeType { name, .. }):

#[allow(unused_mut)]
let mut name: String = "".to_string();

...

if let Ok(value) = result {
  name = value
}

...

Ok(Book { name: name })

After:

#[allow(unused_mut)]
let mut __name_value: String = "".to_string();

...

if let Ok(value) = result {
  __name_value = value
}

...

Ok(Book { name: __name_value })

Issue #21

[coveralls]

Pull Request Test Coverage Report for Build 93

• 11 of 23 (47.83%) changed or added relevant lines in 3 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.2%) to 36.549%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
yaserde_derive/src/de/expand_struct.rs	0	12	0.0%

Totals
Change from base Build 92:	0.2%
Covered Lines:	682
Relevant Lines:	1866

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💛 - Coveralls

[MarcAntoine-Arnaud]

thank you @DmitrySamoylov for the improvement !