doc: fix typos (#96)

Misuse of "lets".

Co-authored-by: Luis Saiz <luis.saiz@bbva.com>

docs/source/the_project/quickstart.rst

@@ -76,7 +76,7 @@ Reasons:
 Using Kapow! (spoiler: it's the winner!)
 ++++++++++++++++++++++++++++++++++++++++
 
-Ok, lets analyze **Kapow!** and check if it is compatible with our constraints:
+Ok, let's analyze **Kapow!** and check if it is compatible with our constraints:
 
 1. **Kapow!** is Open Source, so **it's also free as in beer**.
 2. By using kapow! we don't need to program our own solution, so we **don't have to waste time**.
@@ -148,7 +148,7 @@ et voilà !
 Under the Hood
 ++++++++++++++
 
-To understand what's happening under the hood with **Kapow!** lets see the
+To understand what's happening under the hood with **Kapow!** let's see the
 following diagram:
 
 .. image:: /_static/sequence.png

docs/source/tutorial/tutorial02.rst

@@ -16,7 +16,7 @@ What we've done?
 
 **Senior**
 
-  Sure!  Lets take a look at the documentation to see how can we tweak with the
+  Sure!  Let's take a look at the documentation to see how can we tweak with the
   logic of the request.
 
 **Junior**