Run rustfmt check on CI (wasmi-labs#154)

* Run rustfmt check on CI

* Reformat.

.travis.yml

@@ -22,7 +22,9 @@ env:
 
 install:
 - if [ "$TRAVIS_RUST_VERSION" == "nightly" ]; then rustup target add wasm32-unknown-unknown; fi
+- rustup component add rustfmt
 script:
+- cargo fmt --all -- --check
 # Make sure nightly targets are not broken.
 - if [ "$TRAVIS_RUST_VERSION" == "nightly" ]; then cargo check --tests --manifest-path=fuzz/Cargo.toml; fi
 - if [ "$TRAVIS_RUST_VERSION" == "nightly" ]; then cargo check --benches --manifest-path=benches/Cargo.toml; fi

src/memory.rs

@@ -184,7 +184,7 @@ impl MemoryInstance {
     }
 
     /// Returns current used memory size in bytes.
-	/// This is the highest memory address that had been written to.
+    /// This is the highest memory address that had been written to.
     pub fn used_size(&self) -> Bytes {
         Bytes(self.buffer.borrow().len())
     }
@@ -392,9 +392,9 @@ impl MemoryInstance {
         let (read_region, write_region) =
             self.checked_region_pair(&mut buffer, src_offset, len, dst_offset, len)?;
 
-		if dst_offset < self.lowest_used.get() as usize {
-			self.lowest_used.set(dst_offset as u32);
-		}
+        if dst_offset < self.lowest_used.get() as usize {
+            self.lowest_used.set(dst_offset as u32);
+        }
 
         unsafe {
             ::core::ptr::copy(
@@ -435,9 +435,9 @@ impl MemoryInstance {
             )));
         }
 
-		if dst_offset < self.lowest_used.get() as usize {
-			self.lowest_used.set(dst_offset as u32);
-		}
+        if dst_offset < self.lowest_used.get() as usize {
+            self.lowest_used.set(dst_offset as u32);
+        }
 
         unsafe {
             ::core::ptr::copy_nonoverlapping(
@@ -478,9 +478,9 @@ impl MemoryInstance {
             .checked_region(&mut dst_buffer, dst_offset, len)?
             .range();
 
-		if dst_offset < dst.lowest_used.get() as usize {
-			dst.lowest_used.set(dst_offset as u32);
-		}
+        if dst_offset < dst.lowest_used.get() as usize {
+            dst.lowest_used.set(dst_offset as u32);
+        }
 
         dst_buffer[dst_range].copy_from_slice(&src_buffer[src_range]);
 
@@ -499,9 +499,9 @@ impl MemoryInstance {
 
         let range = self.checked_region(&mut buffer, offset, len)?.range();
 
-		if offset < self.lowest_used.get() as usize {
-			self.lowest_used.set(offset as u32);
-		}
+        if offset < self.lowest_used.get() as usize {
+            self.lowest_used.set(offset as u32);
+        }
 
         for val in &mut buffer[range] {
             *val = new_val