Fixes for serialization

[peterzhu2118]

Commit 1: Refactors setting options to a separate method in Liquid::Template which is reused for deserialization.

Commit 2: Freeze blocks in reverse order of creation. Serialization requires the blocks are frozen in reverse order from when it's created (because it requires that the child is frozen before the parent is frozen).

[dylanahsmith]

Commit 2: Freeze blocks in reverse order of creation. Serialization requires the blocks are frozen in reverse order from when it's created (because it requires that the child is frozen before the parent is frozen).

We should try to avoid relying on the correctness of ruby code to avoid crashes (or C assertion failures which will be crashes outside of development). If I revert this commit and test against Shopify/liquid-c#138, then I get the following error in development (or a crash with DEBUG=false)

Assertion failed: (tag_markup->block_body->compiled), function document_body_write_tag_markup, file ../../../../ext/liquid_c/document_body.c, line 96.
rake aborted!

[peterzhu2118]

Yeah, the problem is that the freeze method is also responsible for writing the blocks to the buffer, and the blocks right now are required to be written in reverse order of creation (so the child is written before the parent because the parent needs to know the offset in order to reference the child). The assertion is there to ensure that this condition is met.

It might be possible to recursively freeze unfrozen children in liquid-c before the parent itself is frozen. But I think that's additional complexity that doesn't need to be there.

[dylanahsmith]

That is a debug assertion though. We could raise instead

[peterzhu2118]

I changed it to raise an error instead of an assertion error in Shopify/liquid-c@61e88b3. The error looks like this:

RuntimeError: child #<Liquid::C::BlockBody:0x00007fdb108278f8> has not been frozen before the parent