fix validation for tag on multiple lines

[francescobarbera]

When a tag is split into multiple lines, validation fails.
For example

<name
attribute1="attribute1"
attribute2="attribute2"
/>

is considered invalid.

To solve this issue, I add a check also for new line characters.

[coveralls]

Coverage remained the same at 97.198% when pulling b6b2f9f on francescobarbera:master into 65c39be on NaturalIntelligence:master.

[amitguptagwl]

Thanks for your changes.