Convert all assert!s not documented as panics into debug_assert!s.

Document the rest.

src/phy/pcap_writer.rs

@@ -63,6 +63,9 @@ pub trait PcapSink {
     /// Write the libpcap packet header into the sink.
     ///
     /// See also the note for [global_header](#method.global_header).
+    ///
+    /// # Panics
+    /// This function panics if `length` is greater than 65535.
     fn packet_header(&self, timestamp: u64, length: usize) {
         assert!(length <= 65535);
 

src/storage/assembler.rs

@@ -54,7 +54,7 @@ impl Contig {
     }
 
     fn shrink_hole_to(&mut self, size: usize) {
-        assert!(self.hole_size >= size);
+        debug_assert!(self.hole_size >= size);
 
         let total_size = self.total_size();
         self.hole_size = size;