Remove empty lines from html file by using ERB trim_mode flag

[benoittgt]

Close: #759

As mentioned in #759, I saw that rdoc is generating extra empty lines. This PR try to reduce the amount of empty lines to have a cleaner html structure.

The impact of this PR can be seen on rspec-core gem documentation : benoittgt/rdoc-rspec-core-no-empty-lines@6b57098

First line of partial templates do not need to have -%> at the end, because it breaks the indentation when they are used in parent template.

[kbrock]

fwiw/ in erb, I tend to not bother with the <%- if it is at the beginning of the line with no indentation. But I tend to always have -%> at the end of the line. Noticed you're not using skip at the end of the line. reason for this?

(btw/ <3 the PR )

[benoittgt]

Hello @kbrock

Thanks for your kind words. You are completly correct for the <%- when it is the begining of the line. I will change that.
What do you mean by "skip"? :)

Is it related to a comment I make:

First line of partial templates do not need to have -%> at the end, because it breaks the indentation when they are used in parent template.

[aycabta]

Great works! I created #760 for this problem after #759 is issued, and you did investigations and created this Pull Request. I'll release a new version of RDoc later.

[kbrock]

@benoittgt adding -%> ignores the trailing "\n"
So it is easier to not add too much white space

glad this got merged